A plot of reactant concentration versus time for a reaction is a straight line with a negative slope giving the rate constant, and the intercept, giving the initial concentration of the reactant. The order of the reaction is

Options

A. 0
B. 1
C. 2
D. none of these

Answer

To determine the order of the reaction based on the information provided, we can follow these steps:

### Step 1: Understand the relationship between concentration and time
In chemical kinetics, the relationship between the concentration of reactants and time can indicate the order of the reaction.

### Step 2: Analyze the given plot
The question states that the plot of reactant concentration versus time is a straight line with a negative slope. This indicates that as time increases, the concentration of the reactant decreases linearly.

### Step 3: Identify the order of the reaction
For a reaction to have a straight-line plot of concentration versus time, it is indicative of a **zero-order reaction**. In a zero-order reaction, the rate of reaction is constant and does not depend on the concentration of the reactant. The rate law for a zero-order reaction can be expressed as:
\[ \text{Rate} = k \]
where \( k \) is the rate constant.

### Step 4: Relate the slope and intercept to the reaction order
In a zero-order reaction, the concentration of the reactant decreases linearly over time, and the equation can be expressed as:
\[ [A] = [A]_0 - kt \]
where:
- \([A]\) is the concentration of the reactant at time \( t \),
- \([A]_0\) is the initial concentration,
- \( k \) is the rate constant,
- \( t \) is time.

From this equation, we can see that the plot of \([A]\) versus \( t \) will yield a straight line with a slope of \(-k\) and an intercept of \([A]_0\).

### Conclusion
Based on the analysis of the plot and the characteristics of the reaction, we conclude that the order of the reaction is **zero-order**.

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