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. 0.3
B. 0.18
C. 0.17
D. 0.11

Answer

D

Explanation

`NH_(4)HS(s) hArr NH_(3)(g) +H_(2)S(g)`
If x is the parital pressure of `H_(2)S` formed at equilibrium
`(p_(NH_(3)))_("eqm.")=(0.50+x)` atm
`(p_(H_(2)S))_(eqm)=x` atm
`(p_(NH_(3)))_(eqm)+(p_(H_(2)S))_(eqm)=0.50+x+x=0.84`
`x=0.17 atm`
`K_(p)=(p_(NH_(3)))_(eqm)xx(p_(H_(2)S))_(eqm)`
`=(0.50+0.17)xx0.17=0.1139=0.11`