The order of reaction may be a fractional number.

Answer

### Step-by-Step Solution:

1. **Understanding the Order of Reaction**:
The order of a reaction refers to the power to which the concentration of a reactant is raised in the rate law expression. It indicates how the rate of reaction is affected by the concentration of the reactants.

2. **Experimental Determination**:
The order of a reaction is not something that can be predicted solely from the balanced chemical equation. Instead, it is determined experimentally. This means that to find out the order, one must conduct experiments and analyze the data.

3. **Possible Values of Order**:
The order of a reaction can take on various values:
- **Positive Order**: Indicates that an increase in the concentration of the reactant increases the rate of reaction.
- **Zero Order**: Indicates that changes in the concentration of the reactant do not affect the rate of reaction.
- **Negative Order**: Indicates that an increase in the concentration of the reactant decreases the rate of reaction.
- **Fractional Order**: It is possible for the order of a reaction to be a fractional number (e.g., 0.5, 1.5). This typically occurs in complex reactions where the relationship between concentration and rate is not straightforward.

4. **Conclusion**:
Therefore, the statement that "the order of reaction may be a fractional number" is true. It reflects the complexity of reaction kinetics and the various ways in which reactants can influence the rate of a reaction.