Reversible reactions and equilibrium

9.Consider the equilibrium: ICl(l) + Cl2(g) ⇌ ICl3(s) (dark brown) (yellow). The forward reaction is exothermic. What is observed when the temperature is increased?

10.In the Haber process (450 °C, 200 atm), if the pressure is increased to 400 atm while keeping the temperature constant, what happens to the percentage of ammonia in the equilibrium mixture?

11.In the Contact process, sulfur trioxide is not absorbed directly into water because:

12.For the reaction 2NO2(g) ⇌ N2O4(g) (brown) (colourless), what colour change occurs if the pressure is increased?

13.For the reversible reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g). The forward reaction is exothermic. Which combination of conditions gives the highest equilibrium yield of SO3?

14.In the Contact process, the main reaction is: 2SO2(g) + O2(g) ⇌ 2SO3(g). The reaction is carried out at a pressure of about 2 atm instead of a much higher pressure. Which is the best reason for using this relatively low pressure?

15.Consider the equilibrium: ICl(l) + Cl2(g) ⇌ ICl3(s) (dark brown) (yellow). The forward reaction is exothermic. The mixture is heated. What is observed and why?

16.For the reaction: 2NO2(g) ⇌ N2O4(g) (brown) (colourless). What colour change occurs if the pressure is increased?

17.A student adds anhydrous cobalt(II) chloride (blue) to water. Which colour change occurs and what does this indicate?

18.In the Haber process, the conditions used are 200 atm, 450 °C, and an iron catalyst. If a new catalyst allowed the same yield of ammonia to be achieved at a lower temperature of 400 °C, what would be the main advantage?

19.For the equilibrium: N2(g) + 3H2(g) ⇌ 2NH3(g), what happens to the unreacted nitrogen and hydrogen after the product ammonia is removed?

20.What is the catalyst used in the Haber process?

21.In an experiment to demonstrate the reversibility of the hydration of cobalt(II) chloride, a student places anhydrous cobalt(II) chloride (blue) in a sealed container with a few drops of water. After some time, the solid turns pink. Which statement explains this observation?

22.Which of the following is the correct colour change when hydrated copper(II) sulfate is heated?

23.Consider the equilibrium: 2SO2(g) + O2(g) ⇌ 2SO3(g). The forward reaction is exothermic. In the Contact process, the main stage is carried out at about 450 °C and 2 atm pressure. Which statement explains why a pressure much higher than 2 atm is not used?

24.In the Haber process, the gases leaving the reactor are cooled. Which substance liquefies and is removed?

25.A student investigates the equilibrium: CoCl2·6H2O(s) ⇌ CoCl2(s) + 6H2O(g). The forward reaction is endothermic. In a closed system at equilibrium, the colour is a mixture of pink and blue. Which change would cause the mixture to become more pink?

26.A reversible reaction is at equilibrium in a closed system. Which statement is always true?

27.In an experiment to determine the effect of concentration on equilibrium, a student adds a few drops of concentrated hydrochloric acid to a green solution containing [Co(H2O)6]2+ ions and Cl- ions. The equilibrium is: [Co(H2O)6]2+(aq) + 4Cl-(aq) ⇌ [CoCl4]2-(aq) + 6H2O(l). The solution turns blue. Which statement explains this?

28.For the equilibrium: 2SO2(g) + O2(g) ⇌ 2SO3(g) (forward reaction exothermic), the equilibrium mixture at a certain temperature contains 96% sulfur trioxide. If the pressure is increased, what will happen to the percentage of sulfur trioxide?

29.In an experiment, a student adds a few drops of concentrated hydrochloric acid to a green solution containing [CoCl4]2- (blue) and [Co(H2O)6]2+ (pink) at equilibrium. The solution turns blue. What does this indicate about the effect of chloride ions on the equilibrium?

30.For the reversible reaction: CH4(g) + H2O(g) ⇌ 3H2(g) + CO(g) (forward reaction endothermic), which combination of temperature and pressure gives the highest yield of hydrogen?

31.In the Contact process, the main reaction occurs at a temperature of 450 °C and a pressure of 2 atm. At this pressure, the equilibrium mixture contains approximately what percentage of sulfur trioxide?

32.Complete the sentence about reversible reactions.

33.In the Contact process, sulfur trioxide is absorbed into concentrated sulfuric acid rather than water. What is the reason for this?

34.Which symbol is used in chemical equations to indicate a reversible reaction?

35.In a reversible reaction, if the forward reaction is exothermic, then the reverse reaction is endothermic.

36.What is the colour of anhydrous cobalt(II) chloride?

37.Which statement about dynamic equilibrium is correct?

38.A catalyst changes the position of equilibrium in a reversible reaction.

39.In the Haber process, what is the source of hydrogen?

40.For the equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), the forward reaction is exothermic. Which change would shift the equilibrium to the left?

41.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. What is the independent variable?

42.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Which observation or quantity is the dependent variable?

43.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Which decision best controls another factor in this comparison?

44.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Why should the class repeat measurements or check multiple comparable observations?

45.A class is evaluating an application of reversible reactions and equilibrium. Which statement identifies a relevant limitation?

46.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Which conclusion is most justified by a controlled comparison?

47.Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Select the two practices that strengthen the validity of this comparison.

48.When evaluating evidence about reversible reactions and equilibrium, select the two scientifically defensible statements.

49.Design a fair investigation for this question: Use a teacher-approved model to compare equilibrium composition at different temperatures in a closed reacting system. Identify what to compare, what to record and one control.

50.Explain one use of the science in reversible reactions and equilibrium and evaluate one limitation of the evidence or application.

51.At equilibrium, product concentration stays constant. What is happening at the particle level?

52.For a reversible exothermic forward reaction, a catalyst is added at constant temperature. What changes?