The first-order reaction $A (g) 2 B (g) + C (g)$ ( $k = 0.03 mi n^{- 1}$ ) starts with pure A at 200 mmHg in a rigid vessel. Find the total pressure in mmHg after 30 min, to the nearest integer. Use $e^{- 0.9} = 0.4066$ .

Numerical answer type, answer in mmHg, tolerance 2.

Answer: 437 mmHg

k t = 0.90

, so A reacted

x = P_{0} (1 - e^{- k t}) = 200 (1 - 0.4066) = 118.7

mmHg. Each unit of A gives three units of gas, so

P_{t} = P_{0} + 2 x = 200 + 237.4 = 437.4 \approx 437

mmHg.