The iodine clock reaction you studied today is considered to be an irreversible
ID: 518490 • Letter: T
Question
The iodine clock reaction you studied today is considered to be an irreversible reaction: when the reactants are converted to products, there is no reverse reaction to re-form reactants from the products. What would happen to the color of the solution if the reaction were reversible? Consider the generic reaction below, where a dilute aqueous solution of "A" reacts with water, the solvent. Explain why, even though water is a reactant, increasing the amount of water is likely to decrease the reaction rate. A(aq) + H_2O(I) rightarrow B(aq) The "strike anywhere" type of matches usually have their tips coated with phosphorus, which makes it easier for them to light with less friction than regular matches. The phosphorus helps initiate the combustion reaction, but it should not be considered to be a catalyst. Why not? Considering the principles of collision theory: Explain why increasing the concentration of reactant increased reaction rate. Explain why increasing temperature lead to increased reaction rates.Explanation / Answer
1. If the reactions were reversible in an iodine clock experiment, the formed end point dark blue color would turn into colorless or become lighter over time. This would show that the reaction has gone to form reactants from products and is reversible.
2. The concentration of water is so high that any change in its concentration does not affect the rate of the reaction as written. The rate is only dependent upon concentration of A in solution and hence increasing amount of water does not affect the reaction.
3. Phosphorous in the ignition gets used up and hence cannot be considered a catalyst which remains unchanged in a reaction.
4. Collision theory
a. Increasing concentration of reactant would enhance the chances of reactants to collide with one another to form products, thus rate of reaction would increase.
b. Increasing temperature increases kinetic energy of molecules and thus molecules move faster and chances of collision goes up, thus formation of products increases. Rate of reaction increases.
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