Question

When `3*06` of solid `NH_(4)HS` is introduced into a two - litre evacuated flask at `27^(@C,`30% of the solid decomposes into gaseous ammonia and hydrogen sulphide.
(i) Calculate `K_(c) and K _(p)` for the reaction at `27^(@)`C.
(ii) What would happen to the equilibrium when more solid `NH_(4)HS` is introduced into the flask ?

Answer 1

` {:((i),NH_(4)HS(s),hArr,NH_(3)(s),+,H_(2)S(g)), ("Intial amount",3*06 g,,,,), (,=3*06//51 "mole",,,,),(,=0*06 "mole",,,,):}`
`{:("At eqm.",0*06-30/100xx0*06,0*018 "mole",0*018"mole"), (,=0*06-0*018,,), (,=0*042 "mole",,):}`
` {:("Eqm.conc",1,0*018//2,0*018//2),(,("being solid"),=0*009,=0*009 "mol"L^(-1)):}`
` K_(c) = ([NH_(3)][H_(2)S])/([NH_(4)HS])=(0*009 xx 0*009)/1 = 8*1 xx10^(-5)" " ( [NH_(4)HS(s)] = 1 ) `
` K_(p) = K_(c) (RT)^(Delta n_(g)) = 2 -0 =2`
(ii) As `K_(c) = [NH_(3)][H_(2)S] ` and does not depend upon the amount of `NH_(4)HS` (s) . hence , there will be no effect on equilibrium when more solid `NH_(4)HS ` is added.