problem solving

Question

Problem 1: For the reaction: H₂O₂ + 3I⁻ + 2H⁺ ⟶ I₃⁻ + H₂O four experiments studying initial concentrations and initial rates are performed. The data are summarized in the table found below.

Answer the questions below:

1. What is the order of this reaction with respect to H₂O₂?
2. What is the order of this reaction with respect to I⁻?
3. What is the order of this reaction with respect to H⁺?

Answer 1

Hi Shelly,

To find the order with respect to each reactant, you want to compare 2 trials in which 2 are held constant while the other changes and then see what happens to the rate.

(1). So, to find the order with respect to H₂O₂, we look at trials 1 and 2 since [H₂O₂] doubles and the others stay the same. The rate doubles also, so it is FIRST ORDER with respect to [H₂O₂]

(2). To find the order with respect to I^-, we look at trials 1 and 3 since [I^-] doubles and the others stay the same. The rate also doubles, so it is FIRST ORDER with respect to [I^-].

(3). To find the order with respect to H⁺, we look at trials 1 and 4 since [H⁺] doubles and the others stay the same. The rate does not change so it is ZERO ORDER with respect to [H⁺].

Hope that makes sense.