Question

For a first order reaction (1) products the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is :

• A. $ext{1.73 × 1} ext{0}^{ ext{-5}} ext{ M/min}$
• B. $ext{3.47 } ext{×} ext{ 1} ext{0}^{ ext{-4}} ext{ M/min}$
• C. $ext{3.47 × 1} ext{0}^{ ext{-5}} ext{ M/min}$
• D. $ext{1.73 } ext{×} ext{ 1} ext{0}^{ ext{-4}} ext{ M/min}$

Answer 1

Answer: (B)

$ext{3.47 } ext{×} ext{ 1} ext{0}^{ ext{-4}} ext{ M/min}$

Answer 2

$K = \frac{1}{40}In\frac{0.1}{0.025} = \frac{1}{40}In4R = K\lbrack A\rbrack^{1}$

$= \frac{1}{40}In4(.01) = \frac{2In2}{40}(0.1)$ = 3.47 × 10–4