Question

The overall order of the following reaction is $KClO_3 + 6FeSO_4 + 3H_2SO_4 \rightarrow KCl + 3Fe_2(SO_4)_3 + 3H_2O$

• A. ten
• B. six
• C. two
• D. three

Hint:

Never assume the order is the sum of coefficients in a balanced equation unless specifically stated that the reaction is elementary. Complex reactions involving many molecules almost always have low orders like 1 or 2.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The order of a reaction is determined experimentally and cannot be determined just by looking at the stoichiometric coefficients of a balanced equation for a complex reaction.
Step 2: Key Formula or Approach:
The stoichiometric equation shows 10 molecules reacting together. However, a reaction with a molecularity higher than 3 is extremely rare. Such reactions occur through several elementary steps.
Step 3: Detailed Explanation:
The reaction between Potassium chlorate and Ferrous sulphate in an acidic medium is a complex redox reaction. Though the balanced equation involves many reactants, the slow, rate-determining step usually involves only a few species. In this specific textbook case, the reaction is experimentally found to follow second-order kinetics.
Step 4: Final Answer:
The overall order is two.