A first-order reaction has an initial reactant concentration of 0.5 mol L^ -1 . After exactly 30 s , the concentration is found to be 5 × 10^ -4 mol L^ -1 . The rate constant for this reaction is:

Question

Quantrex Academy · Accepted Answer

Correct answer: C. 0.2303 s^ -1

For a first-order reaction, the rate constant

k

is given by:

k = \dfrac{2.303}{t} \log \dfrac{[A]_0}{[A]_t}

Given:

[A]_0 = 0.5\text{ mol L}^{-1}

[A]_t = 5 \times 10^{-4}\text{ mol L}^{-1}

t = 30\text{ s}

Substituting the values:

k = \dfrac{2.303}{30} \log \left( \dfrac{0.5}{5 \times 10^{-4}} \right)

k = \dfrac{2.303}{30} \log (10^3)

k = \dfrac{2.303}{30} \times 3

k = \dfrac{2.303}{10} = 0.2303\text{ s}^{-1}

Answer:

0.2303\text{ s}^{-1}

A first-order reaction has an initial reactant concentration of 0.5...

Options

Correct answer

Step-by-step solution

More from Chapter