The minimum mass of NH₄HS(s) needed to establish equilibrium in the same evacuated vessel at the sam — Chemical Equilibrium Chemistry Question

💡 Solution & Explanation

From the previous sub-question, the equilibrium pressure of NH₃ in an evacuated vessel is 250 mm. Moles of NH₃ gas = PV / RT. P = 250 / 760 atm, V = 5.0 L, R = 0.0821 L·atm/(mol·K), T = 300 K. Moles of NH₃ = (250/760 × 5) / (0.0821 × 300). By stoichiometry, 1 mole of NH₃ comes from 1 mole of NH₄HS. Minimum mass required is when exactly this many moles have dissociated. Molar mass of NH₄HS = 14 + 4 + 1 + 32 = 51 g/mol. Minimum mass = Moles × 51 = (250 × 5 × 51) / (760 × 0.0821 × 300) g. Therefore, correct answer is C.