Factors Affecting Equilibrium C
Aperçu
Seal a little brown gas into a glass tube, drop the tube into iced water, and the colour drains away to almost nothing. Lift it out, warm it in your hand, and the brown floods back. Nothing has been added and nothing has escaped. The same atoms are in the tube the whole time, and yet the tube behaves as though you had a dial on it. That dial is what this lesson is about.
Reversible reactions running in a sealed container settle into a standoff called equilibrium, and the striking thing is that the standoff can be pushed. Change the temperature and you change how much product you end up with. Change the pressure of a gas mixture and you change it again, but only if you have counted the molecules in the equation first. By the end you will be able to look at an unfamiliar reversible reaction, predict which way it moves when the conditions change, and explain the awkward compromise every chemical plant in the world has to make between getting a lot of product and getting it quickly.
Objectifs
- When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
- The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
- If the temperature is raised: the yield from the endothermic reaction increases; the yield from the exothermic reaction decreases. If the temperature is lowered: the yield from the endothermic reaction decreases; the yield from the exothermic reaction increases.
- In gaseous reactions: an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction; a decrease in pressure will favour the reaction that produces the greatest number of molecules as shown by the symbol equation for that reaction.
- These factors, together with reaction rates, are important when determining the optimum conditions in industrial processes, including the Haber process.
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Félicitations, vous avez terminé la leçon sur Factors Affecting Equilibrium C. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
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Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- A reversible reaction in a closed system has reached equilibrium. Which statement is correct? A. Both the forward and the reverse reactions have stopped. B. The amounts of reactants and products in the mixture are equal. C. The forward and reverse reactions are taking place at the same rate. D. All of the reactants have been converted into products. Answer: C
- The forward reaction in a reversible reaction is exothermic. What happens to the yield of the products of the forward reaction when the temperature is raised? A. It increases. B. It decreases. C. It stays the same. D. It increases and then decreases. Answer: B
- For which equilibrium will an increase in pressure increase the amount of product formed? A. H2(g) + I2(g) in equilibrium with 2HI(g) B. N2(g) + 3H2(g) in equilibrium with 2NH3(g) C. CH4(g) + H2O(g) in equilibrium with CO(g) + 3H2(g) D. 2NH3(g) in equilibrium with N2(g) + 3H2(g) Answer: B
- What is the effect of adding a catalyst to a reaction mixture that is at equilibrium? A. The yield of the product increases. B. The position of equilibrium moves to the right. C. The position of equilibrium is unchanged but equilibrium is reached more quickly. D. The forward reaction is speeded up more than the reverse reaction. Answer: C
- Ammonia is manufactured at about 450 degrees Celsius even though a lower temperature would give a greater yield. Why is the higher temperature used? A. The reaction would not happen at all at a lower temperature. B. A lower temperature would move the position of equilibrium to the left. C. A lower temperature would make the reaction too slow to be economic. D. The iron catalyst only works above 400 degrees Celsius. Answer: C
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