SCH4U Le Chatelier’s Principle Worksheet For each of the following, indicate the direction the equilibrium would shift and what would happen to the concentrations of each substance in equilibrium. 1. What would be the effect of each of the following on the following equilibrium with carbon dioxide and steam: CO(g) + H2O(g) ↔ CO2(g) + H2(g) + heat a.) b.) c.) d.) e.) The addition of more H2O? The removal of some H2? Raising the temperature? Increasing the pressure? Addition of a catalyst? 2. What would be the effect of each of the following on the equilibrium involving the synthesis of methanol: CO(g) + 2H2(g) ↔ CH3OH(g) a.) b.) c.) d.) The removal of CH3OH? An increase in pressure? Lowering the concentration of H2? The addition of a catalyst? 3. A small percentage of nitrogen gas and oxygen gas in the air combine at high temperatures found in automobile engines to produce NO(g), which is an air pollutant: N2(g) + O2(g) + heat ↔ 2NO(g) a.) Higher engine temperatures are used to minimize carbon monoxide production. What effect does higher engine temperatures have on the production of NO(g)? Why? b.) What effect would high pressures have on the production of NO(g)? Why? 4. What would be the effect of each of the following on the equilibrium involving the reaction of coke (C(s)) with steam to give CO(g) and H2(g): C(s) + H2O(g) ↔ CO(g) + H2(g) a.) b.) c.) d.) The addition of steam? An increase in pressure? The removal of H2 as it is produced? The addition of a catalyst? 5. The binding of oxygen to hemoglobin (Hb), giving oxyhemoglobin (HbO2) is partially regulated by the concentration of H+ and CO2 in the blood. The complex equilibrium can be summarized as: HbO2 + H+ + CO2 ↔ CO2HbH+ + O2 According to Le Chatelier’s principle, what would be the effect of each of the following on the equilibrium: a.) The production of lactic acid (contains H+) and CO2 in a muscle during exercise? b.) Inhaling fresh oxygen enriched air? SCH4U Case Study: The Haber Process Ammonia is one of the world’s most important chemicals, in terms of the quantity manufactured. Some ammonia is processed into nitric acid and various polymers. Roughly 80% of ammonia is used to make fertilizers, such as ammonium nitrate. In the Haber process for manufacturing ammonia, nitrogen and hydrogen combine in the presence of a catalyst. N2(g) + 3 H2(g) ↔ 2 NH3(g) + 92 kJ/mol Kc = 0.40 at 500°C 1a. Predict, qualitatively, the conditions under which the reaction would be spontaneous. Explain your reasoning. 1b. For this reaction, S = - 198 J/mol·K. Explain how the balanced chemical equation can be used to predict the sign of the entropy change. 1c. Calculate the temperature at which the reaction is spontaneous. Hint: What is the value of G for a spontaneous reaction? 1d. What are the trade-offs of carrying out an industrial reaction at a lower temperature? 2. A reaction vessel contains the following concentrations of gases at 500°C: [N2(g)] = 0.10 mol/L, [H2(g)] = 0.30 mol/L, and [NH3(g)] = 0.20 mol/L. a. Is this mixture of gases at equilibrium? b. If not, in which direction will the reaction proceed in order to reach equilibrium? 3. Explain how each of the following factors affect the position of equilibrium and their effect on the yield of ammonia. a. b. c. d. e. temperature pressure volume presence of reactants and products presence of a catalyst 4. Why is it important to maximize the extent of the reaction? 5. What other factors must be considered, in addition to maximizing the extent of reaction, when designing a manufacturing process?
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