Influence of Ionic Strength on Reaction Rates
Explain the effect of ionic strength on rate of reaction.
Ionic strength changes the rate of reaction by changing the electrostatic interactions between reactants and change the rate-determining steps of the reaction. High ionic strength can increase or decrease rate of reaction depending on the type of reaction and the nature of the ions involved.
Ionic strength is considered as concentration of ions in solution, which can significantly affect the rate of chemical reactions. It is an important parameter to understand the kinetics of a reaction because it can significantly change the rate at which reactants are converted into the products.
When an ionic compound is dissolved in water, it dissociates into its constituent ions in the solution. These ions can interact with each other and with other molecules, forming ionic bonds and affecting the overall reactivity of the solution.
At low ionic strength, the number of ions in solution is relatively low. Therefore, the electrostatic interactions between them are weak consequently, reactant molecules collide more frequently which increases the chance of effective collisions and increases the rate of reaction. As the concentration of ions increases, the electrostatic interactions become stronger. Therefore, it is not easy for reactant molecules to overcome this barrier and react. Hence, at higher ionic strengths, the reaction rate decreases.
Furthermore, the presence of ions in solution can affect the stability and reactivity of intermediates formed during a reaction. For example, in the nucleophilic substitution reaction, the intermediate formed can either stabilize or destabilize depending on the ionic strength. At low ionic strength, the intermediate is surrounded by fewer ions, making it more reactive and favoring the reaction. However, at high ionic strength, the intermediate surrounded by more ions and experiences a stronger ionic atmosphere. So, its reactivity decreases and slowing down the reaction.
Can ionic strength impact the equilibrium of a chemical reaction?
Yes, ionic strength can influence the equilibrium of a chemical reaction by shifting the equilibrium position towards the formation of products or reactants. Changes in ionic strength can disrupt the balance between forward and reverse reactions, leading to shifts in equilibrium concentrations.
