Question

The rate of decrease of dissolved oxygen (\(L_t\)) with time \(t\) in a wastewater sample is directly proportional to the amount of oxygen present in the sample at time \(t\). The unit of rate constant \(k\) will be:

• A. \( \text{mol L}^{-1} \)
• B. \( \text{s mol L}^{-1} \)
• C. \( \text{s}^{-1} \)
• D. \( \text{s}^{-1} \text{mol L}^{-1} \)

Hint:

In a first-order reaction, the rate constant k has units of reciprocal time (e.g., s-1).

Answer 1

The Correct Option is C

The equation \( \frac{dL_t}{dt} = -kL_t \) is a first-order reaction.

For a first-order reaction, the unit of \( k \) is \( \text{s}^{-1} \).