Question

The unit of rate constant is per second, the order of reaction is --

• A. Zero
• B. First
• C. Second
• D. Third

Hint:

For a quick check:
0th order: \( \text{mol L}^{-1} s^{-1} \)
1st order: \( s^{-1} \)
2nd order: \( \text{L mol}^{-1} s^{-1} \)

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The unit of the rate constant (\(k\)) depends on the overall order of the reaction (\(n\)).
Step 2: Key Formula or Approach:
The general formula for units of rate constant is:
\[ \text{Units of } k = (mol \cdot L^{-1})^{1-n} \cdot s^{-1} \]
where \(n\) is the order of reaction.
Step 3: Detailed Explanation:
Given unit of \(k = s^{-1}\) (per second).
Matching this with the formula:
\[ (mol \cdot L^{-1})^{1-n} \cdot s^{-1} = s^{-1} \]
This implies the concentration term must be raised to the power of zero.
\[ 1 - n = 0 \implies n = 1 \]
Therefore, the reaction is of the first order.
Step 4: Final Answer:
The order of the reaction is First.