Question

In class we watched a demonstration where the color of the solution oscillated between orange and blue. This is a very complicated reaction with multiple pathways the reaction can take. One pathway can be described as follows:

H₂O₂ + 3 I^- + 2 H⁺ → I₃^- + 2 H₂O

Step 1. H₂O₂ + H⁺ → H₃O₂⁺
Step 2. H₃O₂⁺ + I^- → H₂O + HOI
Step 3. HOI + I^- → OH^- + I₂
Step 4. OH^- + H⁺ → H₂O
Step 5. I₂ + I^- → I₃^-

How many of the following statements are correct based on the information given?
1. I^- is a reactant in this reaction
2. H₃O₂⁺ is a catalyst in this reaction
3. OH^- is an intermediate in this reaction
4. This reaction is third order with respect to I^-
5. I₃^- is a product of this reaction

5
3
2
0
1

Answer is not 1

Answer 1

Since I^- is taking part in left side of the reaction steps, it is a reactant in this reaction.

I^3- is produced in the last step hence, it is a product of the reaction.

Since, OH^- is not shown in overall reaction, it is just an intermediate in this reaction.

There is no mention on the properties of the reaction so we can't actually say if H₂O₂⁺ is acting as a catalyst or not.

Since stoichiometric ration becomes order of the substance only if the reaction is elementary in nature so we can't say for sure that this reaction is 3rd order with respect to I^-.

3 is the correct answer.