9, CHEMICAL EQUILIBRIUM ures in equi A s 260 gram sample of solid ammonium hydro

Question

9, CHEMICAL EQUILIBRIUM ures in equi A s 260 gram sample of solid ammonium hydrogen om of sulfide is placed in an evacuated 3.00-liter container 000 C, at 2n C. After equilibrium is established the total pressure inside the vessel is 0.659 atm. Some solid ammonium hydrogen sulfide remains in the flask. 19 (a) What is the value of the equilibrium constant, K,? (b) What percentage of the solid placed in the flask has reacted? 19 units of to the eq uant ties C ressu of 8.87 bar 300 6.1 uated 19- B If oxide, pre 0.10 m oles 19 ant se Carbon the re 19-89 The decomposition of ammonium hydrogen sulfide is an endothermic reaction. The equation for N the reaction is NH HS(s) NH,(g) HS(g) NH (g)

Explanation / Answer

NH4HS (s) <==> NH3(g) + H2S (g)

Kp = P(NH3) * P (H2O)

As equal amount of NH3 and H2S is formed in the reaction, partial pressure of NH3 and h2S is equal

P(NH3)= P(H2S) = 0.659/2 = 0.3295 atm

Kp = 0.3295 atm * 0.3295 atm = 0.1085

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P = 0.695 atm, V = 3L, T = 25oC = 298 K

Use ideal gas equation to calculate moles of gas present.

n = PV/RT = 0.695 atm * 3L/0.082 L atm/K/mol * 298 K = 0.081 moles

moles of NH3 = moles of H2S = 0.081/2 = 0.04 moles

1 mole NH3 is formed from 1 mol of NH4HS.

moles of NH4HS reacted = 0.04 moles

mass of Nh4HS reacted = 0.04 moles * 51.11g/mol = 2.0444 gm

% reacted = (2.0444/5.260 ) *100 % = 38.87 %

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