Question

Calculate the rate constant of a first-order reaction A giving B + C if the initial pressure of A is 80 mm of Hg. a) 0.020 min⁻1 b) 0.030 min⁻1 c) 0.040 min⁻1 d) 0.050 min⁻1

Answer 1

The rate constant of the first-order reaction A giving B + C is 0.050 min⁻¹. Option D is correct

The rate law for a first-order reaction is:

ate = k[A]

where:

Rate= the change in concentration of A per unit time

k = the rate constant

[A] = the concentration of A

The initial pressure of A = 80 mmHg.

The pressure is proportional to the concentration.

we can substitute 80 mmHg for [A] in the rate law:

Rate = k(80 mmHg)

k = Rate/[A]

Rate = (80 mmHg - 40 mmHg) / 10 minutes

= 4 mmHg/min

k = (4 mmHg/min) / (80 mmHg)

= 0.050 min⁻¹