Kc puzzle HI(g) 700K 54 h_ _ _ _ _ _ _ _ _ _ RHS 0.0185 ?(g) + ?(g) (Reactants) HI(g) 700K 54 h_ _ _ _ _ _ _ _ _ _ RHS Clue – look at phases 0.0185

How can we calculate Kc for a reaction at equilibrium? Key question: How can we calculate Kc for a reaction at equilibrium?

Equilibrium Calculations (1) Hydrogen reacts with iodine to produce hydrogen iodide. At equilibrium there are 0.025 mol of hydrogen, 0.20 mol of iodine and 2.0 mol of hydrogen iodide. Calculate the value of the equilibrium constant, Kc and give its units. What about Kc and the position of equilibrium? What about Kc for the reverse process?

Equilibrium Calculations (2) 200 g of ethyl ethanoate and 7.0 g of water were refluxed together. At equilibrium, the mixture contained 0.25 mol of ethanoic acid. Calculate the equilibrium constant for the hydrolysis of ethyl ethanoate. What about Kc and the position of equilibrium? What about Kc for the reverse process?

Equilibrium Calculations (3) 2 mol of phosphorus(V) chloride vapour are heated to 500 K in a vessel of volume 20 dm3. The equilibrium mixture contains 1.2 mol of chlorine. Calculate the value of the equilibrium constant, Kc for the decomposition of phosphorus(V) chloride into phosphorus(III) chloride. What about Kc and the position of equilibrium? What about Kc for the reverse process?

Equilibrium Calculations (4) 1.0 mol of nitrogen reacts with 1.0 mol of hydrogen in a 2.0 dm3 flask. At equilibrium there are 0.12 mol of ammonia. Calculate the value of the equilibrium constant, Kc and give its units. What about Kc and the position of equilibrium? What about Kc for the reverse process?

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Calculating Kc given the quantity of one component in the mixture at equilibrium

A(aq) + B(aq) C(aq) +D(aq) 5. 1 mol of A and 1 mol of B are allowed to react and come to equilibrium. There is 0.5 mol of A left at equilibrium. Calculate Kc for the reaction.

2HI(g) H2(g) + I2(g) 6. 1 mol of HI(g) was put in a reaction vessel and allowed to come to equilibrium. There was 0.2 mol of HI left in the equilibrium mixture. Calculate Kc.

CH3OH(l) + CH3COOH(l) CH3COOCH3(l) + H2O(l) 7. 2 mol of methanol is reacted with 1 mol of ethanoic acid and allowed to come to equilibrium. In the mixture it was found the 25% of the methanol has reacted. Calculate Kc.

Calculating Kc where the total volume of the system is required

2NO2(g) N2O4(g) 0.5 mol of nitrogen (IV) oxide was allowed to come to equilibrium. The equilibrium mixture contained 0.1 mol of nitrogen (IV) oxide. The total volume of the reaction container was 2dm3. Calculate Kc.

N2(g) + 3H2(g) 2NH3(g) 1 mol of nitrogen gas was mixed with 3 mol of hydrogen gas and the reaction allowed to come to equilibrium. At equilibrium, the mixture contained 1.6 mol of ammonia gas The total volume of the reaction mixture was 5dm3. Calculate Kc.