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. `0.30`
B. `0*18`
C. `0*17`
D. `0*11`

Answer

D

Explanation

`{:(,NH_(4)HS (s),hArr,NH_(3) (g),+,H_(2)S (g)), ("Intial",a " moles",,0.5" atm",,), (" At .eqm.",(a-x),,(0.5+p),,p " atm".):}`
i.e., if x moles of `NH_(4)HS` decompose , increase in pressure due to `NH_(3)` = increase in pressure due to `H_(2)S` = p atm .
Total pressure at equilibrium
` 0.5 + p+ p = 0.5 + 2 p ` atm
` 0.5 + 2 p = 0.84 " atm" or p=0.17` atm
` :. p_(NH_(3)) = 0.5 + 0.17 = 0.67` atm
` p_(H_(2)S) = 0.17 ` atm
` K_(p) =p_(NH_(3)) xx p_(H_(2)S)`
` =0.67 xx 0.17 = 0.1139`