A closed rigid vessel at $400 K$ contains $H X_{2}$ at $2.0 atm$ and $O X_{2}$ at $2.0 atm$ . A spark causes complete reaction of the limiting reagent and the vessel is brought back to $400 K$ , at which all the water formed is in the vapour state. The final total pressure is

Answer: A

At constant

V

and

T

partial pressures are proportional to moles.

2 H X_{2} + O X_{2} 2 H X_{2} O

2.0 atm

H X_{2}

consumes

1.0 atm

O X_{2}

and forms

2.0 atm

H X_{2} O (g)

. Final:

p_{O X_{2}} = 1.0

p_{H X_{2} O} = 2.0

, total

3.0 atm