Bihar Board Class 12 Chemistry Model Paper with Answer 2023

Bihar Board Class 12 Chemistry Model Paper with Answer 2023 Bihar Board Class 12 Chemistry Subjective Questions with Answer

Bihar Board Class 12 Chemistry Subjective Questions with Answer

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ZnO is white when cold, but yellow when hot. Explain.
Zinc oxide is white in colour but on heating, Oxygen leaves as O2 leaving behind Zn2+ and 2 electrons. Zn2+ and the 2 electrons move to the interstitial sites of the crystal . This provides excess electrons in the crystal lattice of ZnO. When light falls on these crystals then these electrons absorb a part of the light in the visible region and hence impart a yellow colour to the ZnO.
ZnO ---heating---> Zn2+ + 1/2O2 + 2e

How many tetrahedral and octahedral voids are there in closed packing of N spheres ?
There are two tetrahedral voids and only one octahedral void for each sphere. If the number of close packed spheres be N.
Then-
No. of tetrahedral voids = 2N
No. of octahedral voids = N

What is Henry's law of solubility ?
Henry's law is one of the gas laws formulated by William Henry in 1803 and states as "at constant temperature, partial pressure of a gas in the vapour phase (p) is proportional to the mole fraction of the gas (X) in the solution.
P ∝ X
Where P = partial pressure of gas
X = Mole fraction of gas in solution
or, P = kH.X
Where kH is called Henry's law constant.

Define Osmosis and Osmotic pressure.
Osmosis is a spontaneous process by which the solvent molecules pass from a solution of low concentration to a solution of high concentration through a semi-permeable membrane. It is of two types. They are Endosmosis and Exosmosis.
Osmotic Pressure is the pressure required to stop the process of osmosis. In other words, we can say that the pressure required to stop the spontaneous flow of solvent molecules from low concentrated solution to high concentrated solution through a semi-permeable membrane.
Osmotic pressure can be calculated using the equation-
π= C S T
where π is the osmotic pressure
C is the molar concentration of the solute
S is the Solution constant
T is the temperature

What is specific conductance ?
The resiprocal of specific resistance (ρ) is called specific conductance.
We know that-
R ∝ l/a
where, l is length of the wire and a is cross sectional area of the wire
or, R = ρ. l/a
or, 1/ρ = 1/R . l/a
or, κ = π . l/a
Unit of κ = ohm−1 . cm/cm2
ohm−1 . cm−1
Its S.I. unit is Sm−1
when, l = 1 and a = 1
then, κ = π
So, specific conductance is the conductance of a conductor of unit length and unit cross sectional area. For electrolytic solutions, the conductance of one cc of the solution is called its specific conductance.

What do you understand by molecularity of a reaction ?
The minimum number of reacting particles (molecules, atoms or ions) that come together or collide in a rate determining step to form product is called the molecularity of a reaction. Molecularity greater than three is generally rare because higher molecularity decreases the chance of their coming together and effective collision to product formation.
Decomposition of H2O2 takes place in the following two steps-
H2O2 → H2O + 1/2O2
Step 1: it is a slow step
H2O2 → H2O + O
Step 2: it is a fast step
O + O → O2
We know that the slowest step is rate-determining. So,from step-1 it is a unimolecular.

What do you understand by physical and chemical adsorption ?
If accumulation of gas on the surface of a solid occurs on account of weak van der Waals' forces, the adsorption is termed as physical adsorption or physisorption. When the gas molecules or atoms are held to the solid surface by chemical bonds, the adsorption is termed chemical adsorption or chemisorption. The chemical bonds may be covalent or ionic in nature. Physisorption is not specific in nature while chemisorption is highly specific in nature. Low temperature favour physisorption while high temperature favour chemisorption.

Write the name and chemical formula of two chief ores of Zinc.
The two chief ores of zinc are calamine ore and zinc blende.
The chemical compound present in calamine is zinc carbonate (carbonate ore) and its chemical formula is ZnCO3.
The chemical compound present in zinc blende is zinc sulphide (sulphide ore) and its chemical formula is ZnS.

Write the formula and structure of pyrophosphoric acid.
Pyrophosphoric acid, also known as diphosphoric acid and its molecular formula is H4P2O7 and structure is given below.
Pyrophosphoric acid

Write two uses of Ozone.
Two uses of ozone is given below-
1. Ozone is used for air purification at crowded places like cinema halls, tunnels, railways, etc.
2. In sterilizing drinking water by oxidising all germs and bacteria.

Arrange HF, HCl, HBr and HI in the increasing order of their acidic strength.
Increasing order of acid strength of the given acids is
HF < HCl < HBr < HI

What are preservatives of food ? Give examples.
Food preservatives are Chemical substances that stop or slow down the growth of bacteria in foods to prevent or delay to spoil the food are called food preservatives. Benzoates, sulphates, Propionates, Nitrates, Vegetable oil, Table salt and Sorbates are generally used as food preservative.

Write one use of the following:
(A) Paracetamol
(B) Tincture of iodine

Paracetamol is used to bring down the body temperature during high fever.
Tincture of iodine (2-3% solution of iodine in alcohol and water) is used as an antiseptic.

Amino acids are amphoteric. Explain.
Amino acids have both acidic (-COOH) and basic (-NH2) group in the same molecule. In the aqueous solution the acidic group losses proton while basic group accepts that proton consequently zwitter ion formed.
Zwitter ion
This zwitter ionic form of α amino acid shows amphoteric behaviour, i.e. act both as acid and base.

Write structural formulae of the following compounds :
(A) N-Ethylethanamine
(B) N, N- Dimethylmethanamine

Structural formulae of N-Ethylethanamine and N, N- Dimethylmethanamine are given below-
N-Ethylethanamine and N, N- Dimethylmethanamine

What is Hell Volhard Zelinsky (HVZ) reaction ?
Carboxylic acids react with chlorine or bromine in presence of small amount of red phosphorous to give alpha halo carboxylic acids. For Hell Volhard Zelinsky reaction molecule must have at least one α hydrogen atom.
Example- R-CH2-COOH ---P/Br2---> R-CHBr-COOH
Mechanism-

Hell Volhard Zelinsky (HVZ) reaction

Write the name of two reagents which is capable of converting – C=O group to >CH2 group.
Clemmensen reduction and Wolf-Kishner Reduction are used to convert a carbonyl group(C = O) into -CH2 group.
In Clemmensen reduction, carbonyl group(C = O) converted into -CH2 group by Zinc amalgam in acidic medium while in Wolf-Kishner Reduction carbonyl group(C = O) converted into -CH2 group by Hydrazine in basic medium.

Write the names and formulae of two compounds which are obtained by the polymerisation of Acetaldehyde.
Acetaldehyde on polymerization gives paraldehyde which is trimer of acetaldehyde and metaldehyde which is tetramer of acetaldehyde. The molecular formula of paraldehyde is C6H12O3 and that of metaldehyde is C8H16O4.

What is power alcohol ? Write its uses ?
Power alcohol is a mixture of 20% absolute alcohol, 80% petrol and a small amount of benzene. It is used as a fuel in automobiles.

What is Markownikoff's rule ?
In unsymmetrical alkenes or alkynes, the positive part of the reagent goes to that multiple bonded carbon atom which has largest number of hydrogen atom(s).
CH3-CH = CH2 + HX → CH3-CH(X)-CH3

What happens when –
A. Chlorine gas reacts with NaOH ?
B. Nitric acid reacts with Zn or Cu at different concentrations ?


A. Cl2 gas react with hot and cold NaOH
a. With hot concentrated NaOH, Sodium chlorate and Sodium chloride forms.
Cl2 + NaOH → NaClO3 + 5NaCl + 3H2
b.With cold NaOH, Sodium hypochlorite and Sodium chloride forms.
Cl2 + 2NaOH → NaCl + NaOCl + H2O

B. Nitric acid reacts with Zn or Cu at different concentrations
Reaction of zinc with Nitric Acid-
Zinc reacts with dilute HNO3 to form Zinc nitrate and Nitrous oxide.
Zn + 10HNO3 → 4Zn(NO3)2 + N2O + 5H2O
Zinc reacts with concentration HNO3 to form Zinc nitrate and Nitrogen dioxide.
Zn+4HNO3 → Zn(NO3)2 + 2NO2 + 2H2O

Reaction of Copper with Nitric Acid-
Copper reacts with concentrated HNO3 to form copper nitrate and nitrogen dioxide.
Cu + 4HNO3 = Cu(NO3)2 + NO2 + H2O
Copper reacts with dilute HNO3 to form copper nitrate and nitric oxide.
3Cu + 8HNO3 = 3Cu(NO3)2 + 2NO + 4H2O

How does Zn react with H2SO4 ?
Zn reacts with both the dilute and concentrated sulphuric.
Zinc liberate hydrogen gas at room temperature when it reacts with dilute sulphuric acid
Zn + H2SO4 → ZnSO4 + H2
Sulphur dioxide along with zinc sulphate formed when Zn is heated with concentrated sulphuric acid.
Zn + 2H2SO4 → ZnSO4 + SO2 + 2H2O

How Acetic acid is obtained from Methyl cyanide ?
Acetic acid is obtained from methyl cyanide by hydrolysis.
CH3CN ---H+---> CH3COOH
Methyl Cyanide     Acetic Acid

Differentiate between Methanoic acid and Ethanoic acid
Methanoic acid and Ethanoic acid can be differentiate by these chemical tests-
A. Methanoic acid gives silver mirror test with Tollen's reagent , whereas ethanoic acid does not give that test.
HCOOH + 2[Ag(NH3)2]+ + 2OH → 2Ag↓ + 2H2O + CO2 + 4NH3
B. Methanoic acid gives white precipitate with mercuric chloride solution but not Ethanoic acid.
HCOOH + HgCl2 → Hg2Cl2 + CO2 + 2HCl

How will you separate 1°, 2° and 3° alcohol by Lucas test ?
Lucas reagent is the mixture of conc. HCl and ZnCl2.
R – OH + HCl ---ZnCl2---> R – Cl + H2O
The solution of 3° alcohol turns turbid and forms an oily layer immediately when Lucas reagent is added.
The solution of 2° alcohol turns turbid and forms an oily layer after five minutes when Lucas reagent is added.
The solution of 1° alcohol remains colourless unless it is subjected to heat. The solution forms an oily layer when heated.

What are the homogeneous and heterogeneous catalysts ? Explain with examples.
Homogenous Catalysis: Those catalysis in which both reactants and catalysts are in same state, are called homogeneous catalysis.
SO2(g) + O2(g) ---NO(g)---> 2SO3(g)
Heterogeneous Catalysis: Those catalysis in which of reactants and catalysts are in different states, are called heterogeneous catalysis.
N2(g) + 3H2(g) ---Fe(S)---> 2NH3(g)

Potassium permaganate is oxidising agent. Explain it with reactions.
Potassium permaganate is strong oxidising agent. It is acting as oxidising agent in acidic, basic and neutral medium.
Acidic medium-
2KMnO4 + 8H2SO4 + 10KI → 6K2SO4 + 2MnSO4 + 8H2O +5I2
Alkaline medium-
2KMnO4 + H2O + KI → KIO3 + 2KOH + 2MnO2
Neutral medium-
2KMnO4 + H2O → 2KOH + 2MnO2 + 3[O]

What is meant by peptization.
The process of converting a freshly prepared precipitate into colloidal form by the addition of a suitable electrolyte in small amount is called peptization. The electrolyte used in the process is called a peptizing agent.
When the ferric chloride is added to the precipitate of ferric hydroxide, the hydroxide precipitate transfer to the sol by absorbing ferric ions. In other words, Fe3+ is absorbed on Fe(OH)3 and splits into colloids.
Fe(OH)3 + Fe3+ → [Fe(OH)3]Fe+3

Nitrogen forms only NCl3 but phosphorus forms PCl3 and PCl5 both why ?
There is no vacant d-orbital in the outermost orbit of Nitrogen. Thus nitrogen show valency only three. There are valent d-orbitals in the outer most orbit of phosphorus and hence it shows variable valency, 3 in ground state and 5 in excited state. Hence nitrogen forms only NCl3 but phosphorus forms PCl3 and PCl5both.

How are vitamins classified ? Name the vitamin responsible for coagulation of blood.
Vitamins are classified into two groups depending upon their solubility in water and fat.
1. Water soluble vitamins – Vitamin B complex and vitamin C.
2. Fat soluble vitamins – Vitamin A, D, E and K.
Vitamin K is responsible for the coagulation of blood.

SO2 is an oxidising and reducing agent both. Explain.
Valence electron of sulphur is six. In SO2, sulphur is in +4 oxidation state, so it can lose its two more electrons to attain +6 oxidation state. It can also gain four electrons. Therefore it can lose and gain electron and acts as oxidising as well as reducing agent.

How can you separate O-Nitrophenol and P-Nitrophenol from the mixture ?
Boiling point of para-nitrophenol is greater than that of ortho-nitrophenol due to intermolecular and intramolecular hydrogen bond respectively. Hence ortho-nitrophenol and para-nitrophenol are separated by steam distillation process.

What are reducing sugars ?
Carbohydrates which can reduce Tollen’s reagent and give red precipitate with Fehling’s solution are called reducing sugar. All monosaccharides (both aldoses and ketoses) and disaccharides (except sucrose) are reducing sugars.

What is Salt Bridge ?
A salt bridge is a device used in an electrochemical cell for connecting its oxidation and reduction half cells.
The salt bridge usually consists of a strong electrolyte which is further made up of ions and maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.
There are two types of salt bridges that are used in electrochemical cells. They are- Glass Tube Bridge and Filter Paper Bridge.

What are primary cell ?
Write the chemical reaction taking place at anode and cathode in a zinc-carbon dry cell.
Or What are primary cells ? Describe dry cell in short.

In primary cell electrode reaction occurs only once and after some time cell becomes dead, that cell can not reused, or recharged, e.g. mercury cell, nickel cadmium cell, etc.
Dry cell consists of a zinc container which acts as the anode. The cathode is a carbon rod surrounded by a mixture of powdered manganese dioxide and carbon. The reaction occurring at anode and cathode are:
Anode reaction -
Zn(s) → Zn2+(aq) + 2e
Cathode reaction -
2MnO(s) + 2NH4+(aq) + 2e ⇌ Mn2O3 (s) + 2NH3(aq) + H2O(l)

What are secondary a cells or batteries ?
A secondary cells is capable of being charged after discharge again and again. A good secondary cell can undergo a large number of discharging and charging cycles. So we can say that a secondary cell is a rechargeable or reusable.
In charging cycle, the reaction that take place during discharge reversed. In this way, it can store the charge for a long period, hence is also called a storage cell. The most common example of a secondary cell is the lead storage battery.

Explain the following phenomenon with the help of Henry's law.
1. Painful condition known as bends.
2. Feeling of weakness and discomfort in breathing at high altitude.
3. Why soda water bottle kept at room temperature fizzes on opening ?

1. Henry's law represents a relation between solubility of gases in liquid and pressure. Scuba divers when comes towards surface, the pressure gradually decreases. This reduce pressure releases the dissolve gas present in blood and leads to formation of bubbles of nitrogen in the blood. This creates a painful condition by blocking capillaries known as blends.

2. At high altitude atmospheric pressure is low as compared to surface which causes difficulty in breathing. On that condition we feel weakness and discomfort.

3. Soda water bottle kept at room temperature fizzes on opening due to different pressure inside and outside the bottle. When the bottle is opened to air, the partial pressure of CO2 above the solution decreases. As a result, solubility decreases and hence CO, bubbles out.

Explain HF is a liquid, while HCl is a gas.
Intermolecular hydrogen bond is present between HF molecules, due to this they form bigger molecule by adding together, therefore it is in liquid state.

On mixing arsenous sulphide sol and ferric hydroxide sol both get precipitated. Why explain ?
On mixing two oppositely charged lyophobic sol in correct ratio both neutralise each other and get precipitated. This is known as natural coagulation. Thus, on mixing negatively charged arsenous sulphide and positively charged ferric hydroxide both collide get precipitated or coagulated.

Explain coagulation with an example.
The process of aggregation of colloidal particles to from insolube precipitate by addition of suitable electrolyte is called coagultion, e.g. Sulphur sol is negatively charged sol. When NaCl (an electrolyte) added to sulphur sol, then in carrying opposite charge present in sol, i.e. Na+ interact with sulphur sol cause neutralisation leading to their coagulation

What is Tyndall effect ? Why it occurs ?
When a strong converging beam of light is passed through a colloidal solution placed in a dark room, the path of beam gets illuminated with a bluish light, this phenomenon is known as Tyndall effect. This is due to reflection of light by big size particles.

How does the precipitation of colloidal smoke take place in cottrell precipitator ?
In cottrell precipitator, smoke particles (charged) are passed through a chamber containing plates with charge opposite to the smoke particles. Smoke particles lose their charge on the plates and get precipitated.

Write down for the separation of mixture of helium and neon.
When the mixture of helium and neon comes in contact with charcoal at 93K, neon gets completely adsorbed, but helium gets free.

Electron affinity of noble or inert gases is zero. Why ?
Inert or noble gases are highly stable due to their completely filled valence shell and due to this, they do not have capacity to accept electron. Therefore, their electron affinity is zero.

Why do noble gases have comparatively large atomic sizes ?
Noble gases have comparatively large atomic sizes because they have van der Waals' radii only which are expected to have larger magnitude whereas other members of a period have either covalent or metallic radii which are less in magnitude.

Noble gases have higher values of ionisation potential. Explain ?
Ionisation potential of noble gases is higher because noble gases have stable and complete electronic configuration. Therefore, higher amount of energy is needed in remove an electron.

Why is N2 is less reactive at room temperature ?
In the nitrogen molecule (N2), two atoms of nitrogen are linked by triple bord (N = N). Due to small atomic size of the element (atomic radius = 70 pm), the bond dissociation enthalpy is very high (946 KJ per mol). This means that it is quite difficult to cleave or break the triple bond at room temperature. As a result, N2 is less reactive at room temperature.

Oxygen forms O2 but sulphur forms S8, Explain.
Atomic size of oxygen is smaller so it can form σ– bond as well as π– bond between O and O atoms and exists as O2.
Atomic size of sulphur is bigger so it form σ– bond only and can not form π – bond together with s – bond between S and S atoms. To satisfied its valency, it forms S8 molecule in which all sulphur atoms bonded with only σ– bond and exist in crown shape.

What are nucleic acids ? Mention their two important functions.
Nucleic acids: They constitute an important class of biomolecules which are found in the nuclei of all living cells in the form of nucleoproteins (i.e., proteins containing nucleic acid as the prosthetic group). Nucleic acids are the genetic materials of the cells and are responsible for transmission of hereditary effect from one generation to the other and also carry out the biosynthesis of proteins. Nucleic acids are biopolymers (i.e., polymers present in the living system). The genetic information coded in nucleic acids controls the structure of all proteins including enzymes and thus governs the entire metabolic activity in the living organism.
Two important functions of nucleic acids are-
a. Replication: The process by which a single DNA molecule produces two identical copies of itself is called replication.
b. Protein Synthesis: DNA may be regarded as the instrument manual for the synthesis of all proteins present in the cell.

What is the difference between a nucleoside and a nucleotide ?
Nucleoside: A nucleoside contains only two basic components of nucleic acids, i.e., a pentose sugar and a nitrogenous base. It may be represented as Sugar-base.
Depending upon the type of sugar present, nucleosides are of two types . They are- Ribonucleosides and Deoxyribonucleosides.
a. Nucleotides: A nucleotide contains all the three basic components of nucleic acids, i.e., a phosphoric acid group, a pentose sugar and a nitrogenous base. In other words, nucleotides are nucleoside monophosphates.Depending upon the type of sugar present, nucleotides like nucleosides are of two types. They are- Ribonucleotides and Deoxyribonucleotides.

The two strands in DNA are not identical but are complementary. Explain.
Two nucleic acid chains are wound about each other and held together by hydrogen bonds between pairs of bases. The two strands are complementary to each other because the hydrogen bonds are formed between specific pairs of bases. Adenine forms hydrogen bonds with thymine whereas cytosine forms hydrogen bonds with guanine.

What are the different types of RNA found in the cell ?
RNA molecules are of three types and they perform different functions. They are named as messenger RNA (m-RNA), ribosomal RNA (r-RNA) and transfer RNA (t-RNA).

What products are expected when lactose is hydrolysed ?
Lactose (C12H22O11) on hydrolysis with dilute acid yields an equimolar mixture of D-glucose and D-galactose.

Where does the water present in the egg go after boiling the egg.
The boiling of an egg is a common example of denaturation of proteins present in the white portion of an egg. The albumin present in the white of an egg gets coagulated when the egg is boiled hard. The soluble globular protein present in it is denatured resulting in the formation of insoluble fibrous protein.

Why vitamin C cannot be stored in our body?
Vitamin C is a water-soluble vitamin. So, it can not be stored in our body because they are readily excreted in urine.

What are enzymes ?
Life is possible due to the coordination of various chemical processes in living organisms. An example is the digestion of food, absorption of appropriate molecules and ultimately production of energy. This process involves a sequence of reactions and all these reactions occur in the body under very mild conditions. This occurs with the help of certain biocatalysts called enzymes. Almost all the enzymes are globular proteins. Enzymes are specific for a particular reaction and for a particular substrate. They are generally named after the compound or class of compounds upon which they work. For example, the enzyme that catalyses hydrolysis of maltose into glucose is named as maltose.

What is the effect of denaturation on the structure of proteins ?
Proteins are very sensitive to the action of heat, mineral acids, alkalies etc. On heating or on treatment with mineral acids, soluble forms of proteins such as globular proteins often undergo coagulation or precipitation to give fibrous proteins which are insoluble in water. This coagulation also results in the loss of the biological activity of the protein. That is why the coagulated proteins so formed are called denatured proteins.. Chemically, denaturation does not change the primary structure but brings about changes in the secondary and tertiary structure of proteins.

How are vitamins classified ? Name the vitamin responsible for the coagulation of blood.
Vitamins are classified into two groups depending upon their solubility in water or fat.
a. Fat soluble vitamins: Vitamins which are soluble in fats and oils but insoluble in water are kept in this group. These are vitamins A, D, E and K. They are stored in liver and adipose (fat storing) tissues.
b. Water soluble vitamins: B group vitamins and vitamin C are soluble in water so they are grouped together. Water soluble vitamins must be supplied regularly in diet because they are readily excreted in urine and cannot be stored (except vitamin B12) in our body.
Vitamin K is responsible for coagulation of blood.

Why are vitamin A and vitamin C essential to us? Give their important sources.
Deficiency of vitamin A causes Xerophthalmia (hardening of cornea of the eye) and night blindness. So its use is essential to us. It is available in fish liver oil, carrots, butter and milk. It promotes growth and increases resistance to diseases. Vitamin C is very essential to us because its deficiency causes Scurvy (bleeding of gums) and pyorrhea (loosening and bleeding of teeth). Vitamin C increases resistance of the body towards diseases. Maintains healthy skin and helps cuts and abrasions to heat properly. It is soluble in water. It is present in citrus fruits, e.g.,oranges, lemons, amla, tomatoes, green vegetables (Cabbage) chillies, sprouted pulses and germinated grains.

Why do we need to classify drugs in different ways ?
The classification of drugs and the reasons for classification are as follows:
a. On the basis of pharmacological effect: This classification provides doctors the whole range of drugs available for the treatment of a particular type of problem. Hence, such a classification is very useful to doctors.
b. On the basis of drug action: This classification is based on the action of a drug on a particular biochemical process. Thus, this classification is important.
c. On the basis of chemical structure: This classification provides the range of drugs sharing common structural features and often having similar pharmacological activity. (iv) On the basis of molecular targets: This classification provides medicinal chemists the drugs having the same mechanism of action on targets. Hence, it is the most useful to medicinal chemists.

Which forces are involved in holding the drugs to the active site of enzymes ?
One of the following forces can be involved in holding drugs to the active site of enzymes- Ionicbonding, Hydrogen bonding, Dipole − dipole interaction, van der Waals force.
Name a substance which can be used as an antiseptic as well as disinfectant.
Phenol can be used as an antiseptic as well as a disinfectant. 0.2 percent solution of phenol is used as an antiseptic, while 1 per cent of its solution is used as a disinfectant.

What are the main constituents of dettol ?
The main constituents of dettol are chloroxylenol and α-terpineol.

What is tincture of iodine? What is its use ?
Tincture of iodine is a 2 − 3 percent solution of iodine in alcohol − water mixture. It is applied to wounds as an antiseptic.

What are food preservatives?
Food preservatives are chemicals that prevent food from spoilage due to microbial growth. Table salt, sugar, vegetable oil, sodium benzoate (C6H3COONa), and salts of propanoic acid are some examples of food preservatives.

How are synthetic detergents better than soap ?
Soaps work in soft water. However, they are not effective in hard water. In contrast, synthetic detergents work both in soft water and hard water. Therefore, synthetic detergents are better than soaps.

What are biodegradable and non-biodegradable detergents? Give one example of each.
Detergents that can be degraded by bacteria are called biodegradable detergents. Such detergents have straight hydrocarbon chains. For example: sodium lauryl sulphate Detergents that cannot be degraded by bacteria are called non-biodegradable detergents. Such detergents have highly-branched hydrocarbon chains. For example: sodium -4- (1, 3, 5, 7- tetra methyl octyl) benzene sulphonate.

Why do soaps not work in hard water?
Soaps are sodium or potassium salts of long-chain fatty acids. Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum. This is the reason why soaps do not work in hard water.

Explain the cleansing action of soaps.
Soap molecules form micelles around an oil droplet (dirt) in such a way that the hydrophobic parts of the stearate ions attach themselves to the oil droplet and the hydrophilic parts project outside the oil droplet. Due to the polar nature of the hydrophilic parts, the stearate ions (along with the dirt) are pulled into water, thereby removing the dirt from the cloth.

IUPAC Nomenclature of Complex Compounds
[CO(NH3)6]Cl3
hexaamminecobalt (III) chloride

[CO(NH3)5Cl]Cl2
pentaamminechloridocobalt (III) chloride

K3[Fe(CN)6]
potassium hexacyanoferrate (III)

[K3[Fe(C2O4)3]
potassium trioxalatoferrate (III)

K2[PdCl4]
potassium tetrachloridoplatinum (II)

[Pt(NH3)2ClNH2CH3]Cl
diamminechlorido (methylamine) platinum(II) chloride

[CO(NH3)4(H2O)2]Cl3
Tetraamminediaquacobalt(IlI) chloride

K2[Ni(CN)4]
Potassium tetracyanidonickelate(II)

[Cr(en)3]Cl3
Tris(ethane-1,2-diamine) chromium(III) chloride

[Pt (NH 3) Br Cl (N0 3)]
Amminebromidochloridonitrito-N- platinatc(II) ion

[PtCl2(en)2](N03)2
Dichloridobis(ethane-l ,2-diamine) platinum (IV) nitrate

Fe4[Fe(CN)6]3
Iron(III)hexacyanidoferrate(II)

Fe4[Fe(CN)6]3
Iron(III)hexacyanidoferrate(II)

[Zn(OH)4]2-
tetrahydroxozincate(II) ion

[Pt(NH3)6]4+
hexaammineplatinum (IV) ion

K2[PdCl4]
potassiumtetrachloridopalladate(II)

[Cu(Br)4]2-
tetrabromidocuprate (II)

[CO(NH3)6]2 (SO4)3
hexaaminecobalt(III) sulphate

K2[Ni(CN)4]
potassiumtetracyanonicklate (II)

K3[Cr(OX)3]

potassiumtrioxalatochromate(III)

[CO(NH3)5ONO]2+
pentaamminenitrito-O-cobalt(III)

[Pt(NH3)2Cl2]
diamminedichloridoplatinum(II)

[CO(NH3)5NO2]2+
pentaamminenitrito-N-cobalt (III)

[Pt(NH3)2CI (NH2CH3)]Cl
Diammine chlorido (methylamine) platinum (II) chloride

[Ti(H2O)6]3+
Diammine chlorido (methylamine) platinum (II) chloride

[Ni(CO)4]
Tetra carbonyl nickel (0)

Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element ?
Answer: Ag has a completely filled 4d orbital (4d10 5s1 in its ground state. Now, silver displays two oxidation states (+1 and +2). In the +1 oxidation state, an electron is removed from the s-orboital. However, in the +2 oxidation state, an electron is removed from the d-orbital. Thus, the d-orbital now becomes incomplete (4d9). Hence, it is a transition element.

Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why ?
Answer: Mn has the maximum number of unpaired electrons present in the d-subshell (five). Hence, Mn exhibits the largest number of oxidation states, ranging from +2 to +7.

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only ?
Answer: Both oxide and fluoride ions are highly electronegative and have a very small size. Due to these properties, they are able to oxidize the metal to its highest oxidation state.

Why are Mn2+compounds more stable than Fe2+ towards oxidation to their +3 state ?
Answer: Electronic configuration of Mn2+is [Ar]18 3d5. Electronic configuration of Fe2+ is [Ar]18 3d6. It is known that half-filled and fully-filled orbitals are more stable. Therefore, Mn in (+2) state has a stable d5 configuration. This is the reason Mn2+shows resistance to oxidation to Mn3+. Also, Fe2+ has 3d6 configuration and by losing one electron, its configuration changes to a more stable 3d5 configuration. Therefore, Fe2+ easily gets oxidized to Fe+3 oxidation state.

What is lanthanoid contraction? What are the consequences of lanthanoid contraction ?
Answer: As we move along the lanthanoid series, the atomic number increases gradually by one. This means that the number of electrons and protons present in an atom also increases by one. As electrons are being added to the same shell, the effective nuclear charge increases. This happens because the increase in nuclear attraction due to the addition of proton is more pronounced than the increase in the interelectronic repulsions due to the addition of electron. Also, with the increase in atomic number, the number of electrons in the 4f orbital also increases. The 4f electrons have poor shielding effect. Therefore, the effective nuclear charge experienced by the outer electrons increases. Consequently, the attraction of the nucleus for the outermost electrons increases. This results in a steady decrease in the size of lanthanoids with the increase in the atomic number. This is termed as lanthanoid contraction.
Consequences of lanthanoid contraction:
1. There is similarity in the properties of second and third transition series.
2. Separation of lanthanoids is possible due to lanthanide contraction.
3. It is due to lanthanide contraction that there is variation in the basic strength of lanthanide hydroxides. (Basic strength decreases from La(OH)3 to Lu(OH)3.)

Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why ?
Answer: In the first transition series, Cu exhibits +1 oxidation state very frequently. It is because Cu ( +1) has an electronic configuration of [Ar] 3d10. The completely filled d-orbital makes it highly stable.

What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.
Answer: An alloy is a solid solution of two or more elements in a metallic matrix. It can either be a partial solid solution or a complete solid solution. Alloys are usually found to possess different physical properties than those of the component elements. An important alloy of lanthanoids is Mischmetal. It contains lanthanoids (94-95%), iron (5%), and traces of S, C, Si, Ca, and Al.
Uses:
1. Mischmetal is used in cigarettes and gas lighters.
2. It is used in flame throwing tanks.
3. It is used in tracer bullets and shells.

What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements: 29, 59, 74, 95, 102, 104.
Answer: Inner transition metals are those elements in which the last electron enters the f-orbital. The elements in which the 4f and the 5f orbitals are progressively filled are called f-block elements. Among the given atomic numbers, the atomic numbers of the inner transition elements are 59, 95, and 102.

Nitrogen is relatively inert as compared to phosphorus. Why ?
Answer: Because P - P single bond is much weaker than N - N triple bond. The bond length of nitrogen is small and bond dissociation energy is very large which makes it inert and urtreactive. That's why phosphorus becomes more reactive.

Though nitrogen exhibits +5 oxidation state, it does not form pentahalide. Why ?
Answer: Due to non-availability of d-orbitals in its valence electronic configuration nitrogen does not form pentahalide.

What is the basicity of H3PO2 and Why ?
Answer: H3PO2 has one replaceable H atom so it is monobasic.

Bond enthalpy of fluorine is lower than that of chlorine. Why ?
Answer: Because F2 is very small in size and its interelectronic repulsions between the lone pairs of electrons are very large.

On adding NaOH to ammonium sulphate, a colourless gas with pungent odour is evolved which forms a blue coloured complex with Cu2+ ion. Identify the gas.
Answer: The gas with a pungent odour is NH3 and the blue coloured complex is Tetra-ammine copper (II) sulphate monohydrate.

Why is BiH3 the strongest reducing agent amongst all the hydrides of group 15 elements ?
Answer: Reducing nature depends upon the stability of M - H bond. Stability of the bond decreases from N to Bi hydrides, So, BiH3 is the strongest reducing agent.

What is the covalency of nitrogen in N2O5 ?
Answer: The covalency of nitrogen in N2O5 is 4 because each nitrogen atom has four shared electrons pairs.

Fluorine exhibits only -1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also. Why is it so ?
Answer: Because fluorine is the most electronegative element and it does not have vacant d-orbitals.

Why is F2 a stronger oxidising agent than Cl2 ?
Answer: Due to low bond dissociation enthalpy and high electronegativity of Fluorine, it has very strong tendency to accept electrons and get reduced.
F + e → F
That's why, F2 acts as strong oxidising agent than Cl2.

NF3 is an exothermic compound but NCl3 is an endothermic compound. Explain.
Answer: Due to smaller size of F, the N – F bond is much stronger than N – Cl bond while bond dissociation energy of F2 is much lower than that of Cl2. Therefore, energy released during the formation of NF3 molecule is more than the energy needed to break N2 and F2 molecules into atoms.
In other words, formation of NF3 is an exothermic reaction. The energy released during the formation of NCl3 molecule is less than the energy needed to break N2 and Cl2 molecules into atoms. Thus formation of NCl3 is an endothermic reaction.

Why is BiH3 the strongest reducing agent amongst all the hydrides of group 15 elements ?
Answer: Reducing nature depends upon the stability of M - H bond. Stability of the bond decreases from N to Bi hydrides, So, BiH3 is the strongest reducing agent.

Orthophosphoric acid (H3PO4) is non-reducing whereas hypophosphorus acid (H3PO2) is a strong reducing agent.” Explain and justify the above statement with suitable example.
Answer: Orthophosphoric acid is not a reducing agent because it doesn’t have any P-H bond whereas hypophosphorus acid is a strong reducing agent as it has two P-H bonds.

ICl is more reactive than I2.
Answer: I-Cl bond is weaker than I-I bond as a result of which ICl breaks easily to form halogen atoms which readily bring about the reaction, hence ICl is more reactive.

NH3 is a stronger base than PH3.
Answer: Both N and P contain lone pairs of electrons but due to small size and high electronegativity of Nitrogen in NH3, the electron density is much higher than PH3, therefore it can easily donate electrons and acts as strong Lewis base than PH3.

SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed.
Answer: In SF4, due to less steric hindrance by four F atoms, H2O molecules can attack easily while in SF6 the S atom is completely protected by six F atoms and does not allow H2O molecules to attack the S atom.

PbCl4 is more covalent than PbCl2.
Answer: According to Fajan’s rule, high charged cations (Pb4+) can polarise the anion (Cl) more effectively than low charged cations (Pb2+) and hence PbCl4 is more covalent than PbCl2.

At room temperature, N2 is much less reactive.
Answer: Due to presence of triple bonds between two N atoms, their bond length decreases and hence bond dissociation energy increases which makes N2 lesser reactive at room temperature.

Thermal stability decreases from H2O to H2Te.
Answer: Thermal stability decreases from H2O to H2Te due to weakening of bond between hydrogen and the atom from O to Te as size is increasing down the group.

Fluoride ion has higher hydration enthalpy than chloride ion.
Answer: Due to stronger attractions of smaller in size fluoride ion.

Red phosphorus is less reactive than white phosphorus.
Answer: Red phosphorus is less reactive than white phosphorus because white phosphorus possess angle strain where long angles are only 60° making it more reactive.
Also, red phosphorus being polymeric is less reactive than white phosphorus which has discrete tetrahedral structure.

N2O5 is more acidic than N2O3.
Answer: N2O5 is more acidic than N2O3 because higher the oxidation state, higher will be acidic character. In N2O5 N has +5 oxidation state and In N2O3 N has +3 oxidation state.

How the supersonic jet aeroplanes are responsible for the depletion of ozone layer ?
Answer: The oxides of nitrogen released by the exhausts of supersonic jetplanes are causing the depletion of ozone layer.

HF is not stored in glass bottles but is kept in wax-coated bottles.
Answer: HF is highly corrosive and etches glass hence it is kept in wax-coated bottles.

Bleaching of flowers by Cl2 is permanent while that of SO2 is temporary.
Answer: Chlorine bleaches the material by oxidation hence it is permanent while SO2 bleaches the material by reduction and as the material is exposed to air, it gets oxidised and the colour is restored, hence it is temporary.

Bi(V) is a stronger oxidizing agent than Sb(V).
Answer: Bi(V) is a stronger oxidizing agent than Sb(V) due to inert pair effect as the stability of lower oxidation state (+3) increases down the group.

What is rate of reaction also explain the factors affecting it ?
The rate of a reaction tells us to what speed the reaction occurs. Let us consider a simple reaction-
                        R → P
The concentration of R decreases and that of P increases with time. The rate of a reaction is defined as the change in concentration of any of reactant or product with time. As we know that during the progress of a reaction the concentration of R keeps on falling with time. The rate of reaction at any given instant is given by the expression
Rate of reaction = − d[R]/dT
Since the rate of reaction is not uniform throughout the reaction, hence, the rate of disappearance of reactants or rate of appearance of product in small interval of time is given as-
Rate of reaction = − d[R]/dT = + d[P]/dT

Example: 3H2 + N2 = 2NH3
for this reaction, the rate of reaction may be written as:
− 1/3 d[H2]/dT = − d[N2]/dT = + 1/2 d[NH3]/dT

Factors Affecting the Rate of a Chemical Reactions:
There are a number of factors which affect the rate of a reaction, the most important of them are:
Effect of concentration: The rate of a chemical reaction is influenced by the no. of collisions per second between the reacting molecules. On increasing the concentration of the reactant, the number of collisions will increase and the rate of reaction will increase and on decreasing the concentration the rate will decrease.
Effect of nature of reactants: Reactions between polar or ionic molecules occur almost instantaneously. Those reactions in which the bonds are arranged or electrons are transferred takes a comparatively longer time than the reaction between ionic molecules.
Effect of catalyst: A catalyst can increase or decrease the rate of a chemical reaction. For example the combination of hydrogen and oxygen to form water is slow at ordinary temperature, while it proceeds rapidly in presence of platinum.
Effect of surface area of reactant: Surface area of reactants is of importance only for heterogeneous reactions. As particle size decreases, surface area for the same mass increases. The smaller particle thus reacts more rapidly than the larger particles. For example, burning of coal dust in air takes place more rapidly than large lump of coal.
Effect of temperature: With the exception of few reactions, the rate of reaction is increased considerably with an increase of temperature. Generally the rate of a reaction is almost doubled or tribled by an increase of 10oC in temperature.

What is rate constant(k) ?
The proportionality constant of rate equation is called rate constant. It is also called specific rate constant as it has specific value for specific reaction.
Let us consider a chemical reaction-
            R → P
Rate = − d[R]/dT = + d[P]/dT
rate of reaction ∝ [R]
so, the rate law equation: − d[R]/dT = k[R]
            where K is rate constant
When [R] = 1, then-
            − d[R]/dT = k
So, the rate constant k is the rate of the reaction at unit molar concentration of the reactant.

Explain the term order of reaction with example.
The sum of powers of the concentration term in the rate equation of a chemical reaction is called Order of reaction.
Order of reaction obtained from the rate law equation which is obtained experimently.
Let us consider a general chemical reaction-
            nA + mB = Product
then, the rate of reaction = k[A]x [B]y
The value of x and y may or may not be equal to n and m respectively because the value of x and y are determined experimently.
If the reaction takes place in more than one steps, then, the slowest step is rate determining step.
The value of order of reaction may be positive, negative, zero, fraction or integer. The order of reaction can never be more than or equal to the molecularity of the reaction.

Explain the term molecularity with example.
The number of reactant molecules which take part in the formation of activated complex in the slowest step of a chemical reaction is caleed Molecularity of that reaction. Molecularity is a whole number but can never be zero or fraction. Molecularity more than three is generally rare.
Reaction may be uni, bi or ter-molecular depending upon whether one, two or three reactant molecules are involved in the slowest step of a chemical reaction.
Molecularity of a reaction is a theoretical value. So, it is not the real quantity like order of reaction. For a complex reaction, the molecularity of reaction is expressed for each step and hence overall value is meaningless.
2 O3 = 3 O2
O3 → O2 + O       (Fast) (Unimolecular)
O3 + O = 2 O2       (Slow) (Bimolecular)

Derive the rate constant for first order reaction and theit half life period.
The reaction in which rate is determined by the variation of only one concentration term is called first order reaction.
Let us consider the following first order reaction-
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This is the First order kinetics or rate constant for first order reaction.

Half life period (t1/2) for First Order Reaction:
The time during which initial concentration of reactant is reduced to half is called half life period. It is denoted as t1/2
We know that, for first order reaction, the rate constant (k) is-
k = (2.303/t) log(a/a-x) -------1
where a is initial concentration of reactant and (a-x) is concentration after time t.
From equation 1-
t = (2.303/k) log(a/a-x) -------2
Now, when, t = t1/2 then, x = a/2
Now putting the value of t and x in equation 2 we get-
t1/2 = (2.303/k) log2
or, t1/2 = 0.693/k --------3
From the equation 3 we see that half life period is inversely proportional to k and independent of initial concentration of the reactant.

Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.
The phenomenon of accumulation of the molecules of a substance on a solid or liquid surface resulting in the increased concentration of the molecules on the surface is called adsorption. In absorption, the substance is uniformly distributed throughout the bulk of the solution. A distinction can be made by taking an example of water vapours. Water vapours are absorbed by anhydrous calcium chloride but adsorbed by silica gel.

Give reason why a finely divided substance is more effective as an adsorbent.
The extent of adsorption increases with increase in surface area of the adsorbent. Thus, finely divided metals and porous substances having large surface areas are good adsorbents.

What are the factors which influence the adsorption of a gas on a solid?
Factors affecting adsorption of a gas on solids are:
Nature of the adsorbent: The same gas is adsorbed to different extents by different solids at the same temperature. Also, greater the surface area of the adsorbent, more is the gas adsorbed.
Nature of the adsorbate: Different gases are adsorbed to different extents by different solids at the same temperature. Higher the critical temperature of the gas, greater is its amount adsorbed.
Temperature: Since adsorption is an exothermic process, applying Le Chatelier’s principle, we can find out that adsorption decreases with an increase in temperature.
Specific area of the adsorbent: Surface area available for adsorption per gram of the adsorbent increases the extent of adsorption. Greater the surface area, higher would be the adsorption therefore, porous or powdered adsorbents are used.
Pressure: At constant temperature, the adsorption of gas increases with pressure.
Activation of adsorbent: It means increasing the adsorbing power of anadsorbent by increasing its surface area. It is done by:
a. making the adsorbent’s surface rough
b. removing gases already adsorbed
c. subdividing the adsorbent into smaller pi

Why is adsorption always exothermic ?
During adsorption, there is always a decrease in residual forces of the surface, i.e., there is decrease in surface energy which appears as heat. Adsorption therefore, is invariably an exothermic process. In other words, ΔH of adsorption is always negative to keep the value of ΔG negative for the reaction to be spontaneous as ΔS decreases during adsorption.
ΔG = ΔH − TΔS

How are the colloidal solutions classified on the basis of physical states of the dispersed phase and dispersion medium ?
Colloids can be classified into eight types depending upon the physical state of the dispersed phase and the dispersion medium.
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Discuss the effect of pressure and temperature on the adsorption of gases on solids.
Adsorption decreases with an increase in temperature because it is an exothermic process and according to Le Chatelier’s principle the reaction will proceed in backward direction with increase in temperature. However at a constant temperature, adsorption increases with pressure.

What are lyophilic and lyophobic sols ? Give one example of each type. Why are hydrophobic sols easily coagulated ?
There are two types of colloidal sols:
a. Lyophilic sols: The word lyophilic means solvent loving. They are obtained by direct mixing the dispersed phase and the dispersion medium, e.g., sols of gum, gelatin, starch, etc. They are solvent attracting hence quite stable and cannot be coagulated easily.
b. Lyophobic sols: They cannot be prepared by direct mixing the dispersed phase and dispersion medium but are prepared by special methods, e.g., sols of metals. They are solvent repelling. Hydrophobic sols are easily coagulated due to repulsion between water and dispersed phase.

What is the difference between multimolecular and macromolecular colloids? Give one example of each. How are associated colloids different from these two types of colloids ?
Depending upon the type of particles of the dispersed phase, colloids are classified as : multimolecular, macromolecular and associated colloids.
a. Multimolecular colloids: On dissolution, a large number of atoms or smaller molecules of a substance aggregate together to form species having size in the colloidal range (diameter < 1nm). The species thus formed are called multimolecular colloids. For example, a gold sol may contain particles of various sizes having many atoms. Sulphur sol consists of particles containing a thousand or more of S8 sulphur molecules.
b. Macromolecular colloids: Macromolecules in suitable solvents form solutions in which the size of the macromolecules may be in the colloidal range. Such systems are called macromolecular colloids. These colloids are quite stable and resemble true solutions in many respects. Examples of naturally occurring macromolecules are starch, cellulose, proteins and enzymes; and those of man-made macromolecules are polythene, nylon, polystyrene, synthetic rubber, etc.
c. Associated colloids (Micelles): There are some substances which at low concentrations behave as normal strong electrolytes but, at higher concentrations exhibit colloidal behaviour due to the formation of aggregates. The aggregated particles thus formed are called micelles. These are also known as associated colloids. The formation of micelles takes place only above a particular temperature called Kraft temperature (Tk) and above a particular concentration called critical micelle concentration (CMC). On dilution, these colloids revert back to individual ions. Surface active agents such as soaps and synthetic detergents belong to this class. For soaps, the CMC is 10–4 to 10–3 mol L–1. These colloids have both lyophobic and lyophilic parts. Micelles may contain as many as 100 molecules or more.

Why is it essential to wash the precipitate with water before estimating it quantitatively ?
Few impurities which are soluble in water and are adsorbed on the surface of the precipitate are removed by washing them with water.

Comment on the statement that ‘colloid is not a substance but a state of substance’.
Colloid is not a substance, but a state of substance because the same substance may exist as a colloid or crystalloid under different conditions e.g., sulphur. Colloidal solution of sulphur consists of sulphur molecules dispersed in water. In this state, sulphur atoms combine to form multimolecules whose size lies between 1 nm to 1000 nm and form colloidal state. Sulphur forms true solution in carbon disulphide. Similarly soap is a solution at low concentration but a colloid at higher concentration.

Explain the terms with suitable examples: Alcosol, Aerosol and Hydrosol
Alcosol: The sol in which alcohol is used as dispersion medium is called alcosol e.g., sol of cellulose nitrate in ethyl alcohol.
Aerosol: The sol in which dispersion medium is gas and dispersed phase is either solid or liquid, the colloidal system is called aerosol e.g., fog, insecticides, sprays, etc.
Hydrosol: The sol in which dispersion medium is water is called hydrosol e.g., starch sol. a. Alcosol : The sol in which alcohol is used as dispersion medium is called alcosol e.g., sol of cellulose nitrate in ethyl alcohol.

What is solution ?
Solutions are homogeneous mixtures of two or more than two components.

Define the term –solubility ?
The maximum amount of a substance that can be dissolved in a fixed amount of solvent is called its solubility.

What is the effect of pressure on solubility of a gas ?
Solubility is directly related to pressure. So, solubility of a gas increases with increases of pressure.

State Henry’s Law.
Henry’s Law states that at a particular temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas i.e solubility increases with increasing in pressure.

State Raoult’s Law.
Raoult’s Law states that for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction.

What are the factors on which vapour pressure depends ?
The factors on which vapour pressure depends are-
1. Temperature of the liquid.
2. Nature of the liquid.

The vapour pressure of solvent gets lowered, when a non- volatile solute is added to it. Why ?
When a non-volatile solute is added to a solvent, the surface area for escape of solvent molecules decreases and vapour pressure gets lowered.

Name two ways by which vapour pressure of a liquid can be lowered.
The two ways by which vapour pressure can be lowered are –
1. By decreasing the temperature.
2. By adding a non- volatile solute.

How does change in temperature changes the molarity and molality values ?
As the temperature increases, volume increases and molarity decreases whereas molality does not change with any change in temperature.

Define the term colligative properties ?
The properties which depends upon amount of solute and not upon the nature of solute are called colligative properties.

What are the possible deviations from ideal behaviors ?
There are two types of deviation from ideal behaviour possible. The first one is positive and the second one is negative deviations.

Give one example of each deviation ?
Positive deviation – ethanol and acetone.
Negative deviation – chloroform and acetone.

Why is the boiling point elevated when a non – volatile solute is dissolved in a liquid ?
When a non – volatile solute is added, the vapour pressure decreases and the solution is heated to a higher temperature, increasing the boiling point.

How is osmotic pressure of a solution related to its concentration ?
Osmotic pressure, π = CRT
C = concentration, R = gas constant and T= temperature

When does the measurement of colligative property leads to abnormal molecular mass ?
When the solute undergoes either association or disassociation abnormal molar mass is obtained.

When is the value of i less then unity ?
When the solute under goes association in solution, I is less then unity.

Name different types of colligative properties ?
There are four types of colligative properties they are given below–
a) Relative lowering of vapour pressure.
b) Elevation in boiling point.
c) Depression in freezing point.
d) Osmotic pressure.

Give the characteristics of ideal solution ?
An ideal solution is formed from two liquids only when –
a. They obey Raoult’s Law
b. ΔHmix = 0
c. ΔVmix = 0
d. The various inter molecular forces are identical.

A mixture of chlorobenzene and bromobenzene is a nearly an ideal solution but a mixture of chloroform and acetone is not Explain ?
Chlorobezene & bromobenzene both have similar structure and polarity. Therefore the various interactions (solute – solute, solvent – solvent & solute – solvent) are same whereas in chloroform and acetone initially there is no hydrogen bonding but after mixing solute solvent interactions (H –bond ) become stronger and solution deviates from ideal behaviour.

Define the term azeotrope ?
Answer: A solution at certain concentration when continues to boil at constant temperature without change in its composition in solution & in vapour phase is called an azeotrope.