Question

The plot of concentration of the reactant versus time for a reaction is a straight line with a negative slope. This reaction follows

• A. zero order rate equation
• B. first order rate equation
• C. second order rate equation
• D. third order rate equation

Hint:

For a zero-order reaction, the plot of concentration vs time is a straight line having a negative slope.

Answer 1

The Correct Option is A

The question asks us to determine which order of reaction is represented by a concentration versus time plot that yields a straight line with a negative slope. Let's analyze the situation:

1. Understanding Reaction Order: The order of a reaction can be determined by the plot of concentration or logarithm of concentration versus time:

   • Zero-order reaction: The plot of concentration \(([\text{R}])\) versus time \((t)\) is a straight line with a negative slope. The rate equation is given by: [\text{A}] = [\text{A}_0] - kt, where \(k\) is the rate constant.
   • First-order reaction: The plot of the natural logarithm of concentration \((\ln[\text{R}])\) versus time is linear with a negative slope. The rate equation is: \ln[\text{A}] = \ln[\text{A}_0] - kt.
   • Second-order reaction: The plot of the inverse of concentration \(\left(\frac{1}{[\text{R}]}\right)\) versus time is linear with a positive slope: \frac{1}{[\text{A}]} = \frac{1}{[\text{A}_0]} + kt.
   • Third-order reaction: Typically less common and involves a more complex relationship, similar to higher power relations.

2. Analyzing the Given Plot: The question specifies a plot of concentration versus time that is a straight line with a negative slope. This description fits the zero-order reaction characteristics, as explained.

3. Conclusion: According to the characteristics of reaction orders and the information given, the reaction follows the zero-order rate equation. The correct option is:

   Zero order rate equation