Excess solid NH4Cl is placed in an evacuated rigid vessel that already contains NH3(g) at 0.50 atm. At the working temperature K_p = 0.040 atm^2 for NH4Cl(s) NH3(g) + HCl(g). The equilibrium partial pressure of HCl (in atm) is

JEE Advanced levelSingle correct optionDifficulty 3 of 3ce106

Excess solid $NH X_{4} Cl$ is placed in an evacuated rigid vessel that already contains $NH X_{3} (g)$ at 0.50 atm. At the working temperature $K_{p} = 0.040 at m^{2}$ for $NH X_{4} Cl (s) NH X_{3} (g) + HCl (g)$ . The equilibrium partial pressure of $HCl$ (in atm) is

Let

p_{HCl} = x

; then

p_{NH X_{3}} = 0.50 + x

x (0.50 + x) = 0.040

gives

x^{2} + 0.50 x - 0.040 = 0

, so

x = [- 0.50 + 0.25 + 0.16] /2 = 0.0702

atm. Ignoring the initial

NH X_{3}

would give

0.040 = 0.200

atm, which is wrong.