An amount of solid `NH_4HS` is placed in a flask already containing ammonia gas at a certain temperature and 0.50 atm pressure.Ammonium hydrogen sulphide decomposes to yield `NH_3` and `H_2S` gases in the flask.When the decomposition reaction reaches equilibrium, the total pressure in the flask rises to 0.84 atm ? The equilibrium constant for `NH_4HS` decomposition at this temperature is :

Options

A. `0.11`
B. `0.17`
C. `0.18`
D. `0.30`

Answer

A

Explanation

`underset("At emp.")underset("start")(N_(4)HS(s))hArrunderset(0.5+xatm)underset(0.5atm)(NH_(3)(g))+underset(xtam)underset(0atm)(H_(2)S(g))`
Then `0.5+x+x=2x+0.5=0.84` (given)
`impliesx=0.17atm`
`p_(NH_(3))=0.5+0.17=0.67atm,p_(H_(2)S)=0.17atm`
`K=p_(NH_(3))xxp_(H_(2)S)=0.67xx0.17atm^(2)=0.1139=0.11`