Which of the following statements about order of a reaction is true?

Options

A. The order of reaction increases with increase in temperature
B. The order of reaction can be determined from the balanced equation
C. A second order reaction is also bimolecular
D. The order of reaction can only be determined by experiment

Answer

To determine which statement about the order of a reaction is true, let's analyze each of the four statements provided:

1. **The order of the reaction increases with increasing temperature.**
- This statement is not universally true. While temperature can affect the rate of a reaction, it does not necessarily increase the order of the reaction. The order of a reaction is defined by the relationship between the rate of reaction and the concentration of reactants, which does not inherently change with temperature.

2. **The order of the reaction can be determined from the balanced equation.**
- This statement is false. The order of a reaction cannot be determined solely from the balanced chemical equation. It must be determined experimentally, as the order depends on the reaction mechanism and the concentration of reactants.

3. **The second order of the reaction is by moleculars.**
- This statement is misleading. While second-order reactions can involve two reactant molecules, the term "molecularity" refers to the number of reactant particles involved in an elementary reaction step, and it is not synonymous with order. A second-order reaction can arise from a single reactant undergoing a reaction in a way that depends on its concentration squared.

4. **The order of the reaction can only be determined by experiment.**
- This statement is true. The order of a reaction must be determined experimentally, as it is based on the relationship between the rate of reaction and the concentration of reactants, which cannot be inferred from the balanced equation alone.

Based on the analysis, the correct answer is:

**The order of the reaction can only be determined by experiment.**