Question

Identify the order of reaction if the rate constant is k=2×10⁻²s⁻¹:

• A. Zero order
• B. First order
• C. Second order
• D. Half order

Answer 1

The Correct Option is B

The order of a reaction can be determined from the units of the rate constant. In this problem, the rate constant, k, is given as 2×10⁻²s⁻¹.

The units of rate constant for different order reactions are as follows:

• Zero order: mol L⁻¹ s⁻¹
• First order: s⁻¹
• Second order: L mol⁻¹ s⁻¹
• Half order: The units would be unconventional and not commonly used.

Given that the rate constant k has units of s⁻¹, this corresponds to a first order reaction. Therefore, the reaction order is first order.

Answer 2

To determine the order of a reaction, we need to analyze the units of the rate constant (k).

The units of the rate constant (k) are related to the order of the reaction. Here's a quick summary:

• Zero-order: Units of k are mol L^-1 s^-1 or M s^-1.
• First-order: Units of k are s^-1.
• Second-order: Units of k are L mol^-1 s^-1 or M^-1 s^-1.
• Third-order: Units of k are L² mol^-2 s^-1 or M^-2 s^-1.

In this case, the given rate constant is k = 2 × 10^-2 s^-1. The units are s^-1.

Comparing the units with the table above, we can see that the units of the rate constant match those of a first-order reaction.

Therefore, the order of the reaction is first-order.

The correct answer is: Option 2: First order