Question

A certain zero order reaction has rate constant 0.025 M s\(^{-1}\). What will be the concentration of reactant A after 15 seconds if initial concentration is 0.50 M?

• A. 0.060 M
• B. 0.50 M
• C. 0.125 M
• D. 0.375 M

Hint:

In zero order reactions, concentration decreases linearly with time.

Answer 1

The Correct Option is C

Step 1: Write integrated rate law for zero order reaction.
\[ [A]_t = [A]_0 - kt \]
Step 2: Substitute given values.
\[ [A]_0 = 0.50\ \text{M}, \quad k = 0.025\ \text{M s}^{-1}, \quad t = 15\ \text{s} \]
Step 3: Calculate concentration after 15 s.
\[ [A]_t = 0.50 - (0.025 \times 15) \]
\[ [A]_t = 0.50 - 0.375 = 0.125\ \text{M} \]
Step 4: Conclusion.
Concentration of reactant A after 15 seconds is 0.125 M.