Graphite: Preparation, Properties, Structure, Bonding and Uses
NEET ▪ JEE Main & Advanced ▪ JAM ▪ GATE ▪ CSIR-NET ▪ State PSC
1. Preparation of Graphite
| Method | Description | Key Points (Exam-oriented) |
|---|---|---|
| Acheson Process (Industrial) | Most important commercial method • Mixture of calcined petroleum coke + pitch → packed with sand • Electric current passed (graphitization at ~3000°C) • SiC formed as intermediate → decomposes → pure graphite |
▪ Temperature: 2500–3000°C ▪ Reaction: SiO2 + 3C → SiC + 2CO SiC → Si (vapour) + C (graphite) ▪ Frequently asked in JEE & GATE |
| Castner Process (Old method) | Anthracite heated in electric furnace in presence of Cs2 (catalyst) | Rarely asked now |
| Laboratory Preparation | Acid treatment of cast iron → FeC dissolves → graphite remains | NEET sometimes asks source |
Most asked question: The temperature required in Acheson process is approximately 3000°C (True)
2. Structure of Graphite
- Layered structure (Hexagonal lattice)
- Each carbon atom sp² hybridized
- Forms 3 σ-bonds with three neighbouring carbon atoms → hexagonal rings in plane
- Bond angle in the layer is 120° (Trigonal Planar geometry)
- Fourth electron in p-orbital → forms delocalized π-cloud (responsible for electrical conductivity)
- Bond Lengths:
- C–C (in plane) = 1.415 Å (Intermediate between single and double bond).
- Interlayer distance = 3.35 Å (Large gap).
- Layers held by weak van der Waals forces → slippery nature
- Each layer is called graphene (single layer of graphite)
Key Exam Point: In graphite, each carbon is attached to three other carbon atoms → coordination number = 3
Figure 1: The layered structure of graphite showing strong covalent bonds within layers and weak Van der Waals forces between layers.
3. Bonding in Graphite
| Type | Description |
|---|---|
| Covalent bonding | Strong σ-bonds within the layer (sp² hybridisation) |
| Metallic bonding | Delocalized π-electrons → responsible for electrical & thermal conductivity |
| van der Waals forces | Weak forces between layers → low hardness, easy cleavage |
4. Physical Properties of Graphite
| Property | Value / Nature | Reason |
|---|---|---|
| Appearance | Black, shiny, opaque | Delocalized electrons |
| Density | 2.26 g/cm³ | — |
| Melting point | ~3800°C (very high) | Strong covalent network in layers |
| Hardness | Soft (1–2 on Mohs scale) | Weak interlayer forces |
| Electrical conductivity | Good conductor (along the layers) | Delocalized π-electrons |
| Thermal conductivity | High along the plane | Same as above |
| Lubricating property | Excellent lubricant | Layers slide over each other |
| Feel | Slippery, greasy | — |
JEE Favourite: Graphite conducts electricity along the layers but is insulator perpendicular to layers.
5. Chemical Properties
| Reaction | Product | Condition / Note |
|---|---|---|
| Combustion | CO2 | Burns in excess O2 at 700°C |
| With steam (above 1000°C) | Water gas CO + H2 | Used in rockets as moderator also |
| With fluorine (600°C) | Graphite fluoride (CFx) | Highly stable compound |
| Oxidising agents (conc. HNO2 + KClO3) | Graphitic acid (C11H4O5)x (Graphite oxide) | Yellow, interlayer compound |
| Alkali metals (heated) | Intercalation compounds e.g., KC8 (bronze colour) Graphite Intercalation Compounds (GICs) | Used in batteries |
Graphite is thermodynamically more stable allotrope of carbon than diamond at room temperature and pressure.
6. Uses of Graphite (High-Weightage in Exams)
- Electrodes in electric arc furnaces & batteries (good conductor, high m.p.)
- Lubricant (dry & high temperature) – mixed with oil → “graphite grease”
- Moderators in nuclear reactors (slows down neutrons)
- Pencils (“lead” is actually graphite + clay)
- Crucibles & refractory material (high m.p., inert)
- Graphene & carbon nanotubes precursor
- Brushes in electric motors
- Anode in lithium-ion batteries (Li⁺ intercalation)
- Foundry facings, polishing, paints (black pigment)
Most repeated question in NEET/JEE:
“Why graphite is used as lubricant but diamond is not?”
→ Answer: Weak van der Waals forces between layers in graphite allow sliding; diamond has rigid 3D network.
“Why graphite is used as lubricant but diamond is not?”
→ Answer: Weak van der Waals forces between layers in graphite allow sliding; diamond has rigid 3D network.
Quick Comparison: Graphite vs Diamond (Must for Exams)
| Property | Graphite | Diamond |
|---|---|---|
| Hybridisation | sp² | sp³ |
| Structure | Layered | Tetrahedral 3D network |
| Conductivity | Good (along layers) | Insulator (pure) |
| Hardness | Soft | Hardest (10 on Mohs) |
| Density | 2.26 g/cm³ | 3.51 g/cm³ |
| C-C Bond Length | 1.415 Å | 1.54 Å |
| Entropy | High | Low (More ordered) |
| Thermodynamic stability | More stable at RTP | Less stable |
| Lubricant | Use (due to softness) | Does not use (due to hardness) |
Must Read Chemistry of Graphite MCQs asked in NEET, IIT-JEE, IIT-JAM, GATE, CSIR/NET
Related Topics
Graphite: Preparation, Properties, Structure and Uses
Graphite PYQs MCQs
Diamond: Preparation, Properties, Structure and Uses
Diamond PYQs MCQs
Graphene: Preparation, Properties, Structure and Uses
Graphene PYQs MCQs
Fullerenes: Preparation, Properties, Structure and Uses
Fullerenes PYQs MCQs
Carbon Nanotubes: Preparation, Properties, Structure and Uses
Carbon Nanotubes PYQs MCQs