17.1 The Equilibrium Law

A mixture of 1.32 moles of E, 1.49 moles of F and 0.752 moles of G were placed into a 5.0 dm³ container at temperature, T, and allowed to reach equilibrium. At equilibrium, the number of moles of E was 1.86.

Calculate the value of the equilibrium constant, K_c , to 3 significant figures. 

2 E (g) ⇌ 2 F (g) + G (g)        ΔH = -143 kJ mol^-1

Reactants G and H react together to form products J and K according to the equation

3G + H ⇌ 4J + K

A beaker contained 35 cm³ of 0.18 mol dm^-3 of an aqueous solution of G. 

8.41 x 10^-3 moles of H and 3.1 x 10^-3 moles of J were also added to the beaker. The equilibrium mixture contained 4.1 x 10^-3 moles of G. 

Calculate the number of moles of H, J and K at equilibrium.

[5]

Using sections 1 and 2 of the data booklet, calculate the equilibrium constant at 300 K for the oxidation of iron: 

2Fe(s) + O₂ (g) → Fe₂O₃ (s) 
ΔH^Θ = -824.2 kJ mol^{- 1} 
ΔS^Θ = -270.5 J mol^-1

[3]

Diesters are compounds often used as synthetic lubricants for machinery such as compressors. The reaction below shows the formation of a diester from propanoic acid and propane-1,3-diol. 

2CH₃CH₂COOH + HOCH₂CH₂CH₂OH  ⇌  C₉H₁₆O₄ + 2H₂O

At equilibrium, the reaction mixture contained 3.25 moles of CH₃CH₂COOH, 1.15 moles of HOCH₂CH₂CH₂OH, and 1.18 moles of C₉H₁₆O₄.

The value for K_c at temperature, T, is 1.29.

Calculate the concentration of water in the reaction mixture at equilibrium. Give your answer to 3 significant figures. 

[3]

A student deduced that in order to calculate the value of K_c for the reaction in part (a) you must work out the concentrations using the overall volume. 

Is the student correct? Justify your answer.

[2]

Using sections 1 and 2 of the data booklet, determine the value for ΔG for the reverse reaction in part(a) given that temperature T= 30°C. Give your answer, in kJ, to 2 significant figures.

[2]

The reverse reaction in part (a) is slightly endothermic. At a different temperature, T₂, the value for ΔG decreases to -0.52 kJ mol^-1. 

State whether the new temperature, T₂, is higher or lower than the original temperature.
Justify your answer.