Question

1. At equilibrium, the concentrations of reactants and products can be predicted using the equilibrium constant, Kc, which is a mathematical expression based on the chemical equation. For example, in the reaction

aA+bB⇌cC+dD

where a, b, c, and d are the stoichiometric coefficients, the equilibrium constant is

Kc=[C]c[D]d[A]a[B]b

where [A], [B], [C], and [D] are the equilibrium concentrations. If the reaction is not at equilibrium, the quantity can still be calculated, but it is called the reaction quotient, Qc, instead of the equilibrium constant, Kc.

Qc=[C]tc[D]td[A]ta[B]tb

where each concentration is measured at some arbitrary time t.

A mixture initially contains A, B, and C in the following concentrations: [A] = 0.700 M , [B] = 1.20 M , and [C] = 0.400 M . The following reaction occurs and equilibrium is established:

A+2B⇌C

At equilibrium, [A] = 0.590 M and [C] = 0.510 M . Calculate the value of the equilibrium constant, Kc.

2. Calculate the equilibrium concentrations of N2O4 and NO2 at 25 ∘C in a vessel that contains an initial N2O4 concentration of 0.0428 M . The equilibrium constant Kc for the reaction N2O4(g)⇌2NO2(g) is 4.64×10−3 at 25 ∘C.

3. Phosphine (PH3) decomposes at elevated temperatures, yielding gaseous P2 and H2:
2PH3(g)⇌P2(g)+3H2(g) Kp = 398 at 873 K

Part A

If the initial partial pressures are PPH3 = 0.0276 atm , PP2 = 0.863 atm , PH2 = 0.518 atm , calculate Qp.

4. Gaseous indium dihydride is formed from the elements at elevated temperature:
ln(g)+H2(g)⇌lnH2(g)Kp = 1.48 at 973 K
Partial pressures measured in a reaction vessel are:
PIn = 0.0520 atm , PH2 = 0.0370 atm , PInH2 = 0.0740 atm .

Part A

Calculate Qp.

Part B

Determine the direction of reaction to attain equilibrium.

Part C

Determine the equilibrium partial pressure of In.

Express your answer with the appropriate units.

part D

Determine the equilibrium partial pressure of InH2.

Express your answer with the appropriate units.

Part E

Determine the equilibrium partial pressure of H2.

Express your answer with the appropriate units.

The reaction will proceed in the reverse direction to attain equilibrium.

The reaction will proceed in the forward direction to attain equilibrium. 5. The value of Kc for the reaction of acetic acid with ethanol is 3.4 at 25∘C: CH3CO2H(soln)+ C2H5OH(soln)⇌ CH3CO2C2H5(soln)+H2O(soln)Kc=3.4 Acetic acid Ethanol Ethyl acetate 6. At 700 K, Kp = 0.140 for the reaction ClF3(g)⇌ClF(g)+F2(g). Calculate the equilibrium partial pressures of ClF3, ClF, and F2 if only ClF3 is present initially, at a partial pressure of 1.55 atm .

Answer 1