The rate constant of a first order reaction is proportional to the concentration of the reactant.

Explanation

To solve the question regarding the statement "The rate constant of a first order reaction is proportional to the concentration of the reactant," we need to analyze the relationship between the rate constant and the concentration of reactants in a first-order reaction.

### Step-by-Step Solution:

1. **Understanding Rate Constants**:
- The rate constant (k) for any reaction, including first-order reactions, is a proportionality factor that relates the rate of the reaction to the concentration of reactants.

2. **First-Order Reaction Definition**:
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