Question

The reaction AB(aq)->A(g)+ B(g)is second order in AB and has a rate constant of 0.0282 M^{-1} s^{-1} at 25 Celsius. A reaction vessel initially contains 250 mL of 0.105 M AB which is allowed to react to form the gaseous product. The product is collected over water at 25 Celsius.

1-How much time is required to produce 115.0 mL of the products at a barometric pressure of 779.9 mmHg. (The vapor pressure of water at this temperature is 23.8 mmHg.)

Answer 1

I would do this.
Use P = MRT
where P: = (779.9-23.8)/760
and solve for M which should give A and B concns (I assume 0.115L is the volume of the gases).
Take 1/2 that to find M needed for AB and apply the second order equation of
1/A - !/Ao = akt
You know Ao, a = 1, you know k and A (from the calculation). Solve for t which should be i s since k is in s.

Answer 2

is the answer 1392 s?