The dissociation equilibrium pressure of NH₄HS_(s) is 20 cm a 27⁰C. The total pressure at equilibrium when NH₄HS is dissociated in the presence of 15 cm of NH₃ is ------cm

NH₄HS_(s)$\rightleftharpoons$NH_3(g) + H₂S_(g)

given 2p = 20 cm;p = 10 cm; K_p = p² = 100 cm²

let p' is new pressure in presence of 15 cm NH₃

NH₄HS(s)$\rightleftharpoons$NH_3(g) + H₂S_(g)

                       p' +15    p'

100 = (p'+15)(p')

p' = 5 cm

P_total = p'+15+p' = 5+15+5 = 25 cm