Which of the following statemen is /are correct about order of a reaction?
I. The order of a reaction can be a fractional number.
II. Order of a reaction is experimentally determined quantity.
III. The order of a reaction is always equal to the sum of the stoichimetric coefficients of reactants in the balanced chemical equation for a reaction.
IV. The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression.
Choose the correct option.

Options

A. I, II and III
B. I, II and IV
C. II, III and IV
D. All of the above

Answer

To determine which statements about the order of a reaction are correct, let's analyze each statement one by one.

### Step 1: Analyze Statement I
**Statement I:** The order of a reaction can be a fractional number.

**Analysis:** This statement is correct. The order of a reaction can indeed be a fractional number. For example, it can be 1/2, 3/2, etc.

### Step 2: Analyze Statement II
**Statement II:** Order of a reaction is an experimentally determined quantity.

**Analysis:** This statement is also correct. The order of a reaction is determined through experimental data and cannot be predicted solely from the balanced chemical equation. It is based on the rate law derived from experimental observations.

### Step 3: Analyze Statement III
**Statement III:** The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction.

**Analysis:** This statement is incorrect. The order of a reaction is not necessarily equal to the sum of the stoichiometric coefficients. The order is determined by the rate law, which may not correspond to the coefficients in the balanced equation.

### Step 4: Analyze Statement IV
**Statement IV:** The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression.

**Analysis:** This statement is correct. The order of the reaction is indeed the sum of the powers of the concentration terms in the rate law expression. For example, if the rate law is given by rate = k[A]^m[B]^n, then the order of the reaction is m + n.

### Conclusion
Based on the analysis:
- **Correct Statements:** I, II, and IV
- **Incorrect Statement:** III

Thus, the correct option is that statements I, II, and IV are correct.

### Final Answer
The correct statements about the order of a reaction are I, II, and IV.

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