Ammonium sulphide and ammonium selenide on heating dissociates as
`(NH_4)_2S_((s)) hArr 2NH_(3(g)) + H_2S_((g)) , K_(p_1) = 9xx10^(-3) "atm"^3`
`(NH_4)_2Se_((s)) hArr 2NH_(3(g)) + H_2Se_((g)) , K_(p_2) = 4.5xx10^(-3) "atm"^3`
The total pressure over the solid mixture at equilibrium is

Options

A. 0.15 atm
B. 0.3 atm
C. 0.45 atm
D. 0.6 atm

Answer

C

Explanation

`(NH_4)_2Se_((s)) hArr underset(2p)(2NH_(3(g)))+underset"p"(H_2S_((g)))`
`(NH_4)_2Se_((s)) hArr underset"2q"(2NH_(3(g))) + underset"q" (H_2Se_((g)))`
`K_(p_1)=(p_(NH_3))^2 .p_(H_2S)=(2p+2q)^2. p=9.0xx10^(-3)`
`K_(p_2)= (p_(NH_3))^2. p_(H_2Se) = (2p+2q)^2. q= 4.5xx10^(-3)`
`therefore p/q=2 rArr p=2q`
`therefore K_(p_1)=(2p+p)^2 . p = 9.0xx10^(-3)`
`therefore` p=0.1 atm and `q=0.1/2`=0.05
Total pressure = 2p+2q+p+q=3p+3q
= 3 x 0.1 + 3 x 0.05 = 0.45 atm