The Contact Process is an industrial method for producing sulfuric acid ($H_2SO_4$). The key step involves the reversible reaction of sulfur dioxide ($SO_2$) with oxygen ($O_2$) to form sulfur trioxide ($SO_3$):
$2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ $\Delta H = -197 \text{ kJ mol}^{-1}$
This reaction is typically carried out at a temperature of 450°C and a pressure of 1-2 atm using vanadium(V) oxide ($V_2O_5$) as a catalyst. The sulfur trioxide is then absorbed into concentrated sulfuric acid to produce oleum, which is subsequently diluted to form sulfuric acid of the desired concentration.
a. Explain how Le Chatelier’s principle influences the choice of temperature for this reaction in the Contact Process. Justify why a temperature of 450°C is used, considering both equilibrium and rate factors.
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Create Free Account Log inThis is a free VCE Units 3 & 4 Chemistry practice question worth 4 marks, testing your understanding of Le Chatelier’s principle. It falls under How can the rate and yield of chemical reactions be optimised? in Unit 3: How can design and innovation help to optimise chemical processes?. Submit your answer above to receive instant AI-powered marking and personalised feedback.
The global demand for energy and materials is increasing with world population growth. In this unit students investigate the chemical production of energy and materials. They explore how innovation, design and sustainability principles and concepts can be applied to produce energy and materials while minimising possible harmful effects of production on human health and the environment. Students analyse and compare different fuels as energy sources for society, with reference to the energy transformations and chemical reactions involved, energy efficiencies, environmental impacts and potential applications. They explore food in the context of supplying energy in living systems. The purpose, design and operating principles of galvanic cells, fuel cells, rechargeable cells and electrolytic cells are considered when evaluating their suitability for supplying society’s needs for energy and materials. They evaluate chemical processes with reference to factors that influence their reaction rates and extent. They investigate how the rate of a reaction can be controlled so that it occurs at the optimum rate while avoiding unwanted side reactions and by-products. Students conduct practical investigations involving thermochemistry, redox reactions, electrochemical cells, reaction rates and equilibrium systems. Throughout the unit students use chemistry terminology, including symbols, formulas, chemical nomenclature and equations, to represent and explain observations and data from their own investigations and to evaluate the chemistry-based claims of others. A student-designed scientific investigation involving the generation of primary data related to the production of energy and/or chemicals and/or the analysis or synthesis of organic compounds is undertaken in either Unit 3 or Unit 4, or across both Units 3 and 4, and is assessed in Unit 4 Outcome 3. The design, analysis and findings of the investigation are presented in a scientific poster format. School-based assessment The student’s level of achievement in Unit 3 will be determined by School-assessed Coursework. School-assessed Coursework for Unit 3 will contribute 20 per cent to the study score. For each outcome in this unit, students complete at least one task from a specified list. Assessment tasks must be completed mainly in class and within a limited timeframe. External assessment The level of achievement for Units 3 and 4 is also assessed by an end-of-year examination, which will contribute 50 per cent to the study score.
In this area of study, students explore the factors that affect the rate and yield of equilibrium and electrolytic reactions involved in producing important materials for society. Reactants and products in chemical reactions are treated qualitatively through the application of Le Chatelier’s principle and quantified using equilibrium expressions, reaction quotients and Faraday’s Laws. Students explore the sustainability of different options for producing useful materials for society. Outcome 2 On completion of this unit the student should be able to experimentally analyse chemical systems to predict how the rate and extent of chemical reactions can be optimised, explain how electrolysis is involved in the production of chemicals, and evaluate the sustainability of electrolytic processes in producing useful materials for society. Key knowledge
the application of Le Chatelier’s principle to identify factors that favour the yield of a chemical reaction
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