Chapter 3 - Summary Quiz

1. Identify each of the factors that can change a reaction that is at equilibrium?
a) change of pressure
b) change of temperature
c) change in surface area (heterogeneous reaction)
d) addition of a catalyst
e) change of concentration

2. Explain what is meant by the "see-saw" principle when using le Châtelier's principle.

Questions 3 - 10 deal with the reaction: CO2 (g) + 3H2O (l) 2H3O+(aq) + CO32- (aq) for dissolving gaseous carbon dioxide in water.

3. Consider the above reaction.  Which of the following correctly identifies the initial response to the applied stress?

4.  Which of the substances in CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq) can be changed without causing a change in response to the applied stress?
a) CO₂ (g)
b) 3H₂O (l)
c) 2H₃O⁺(aq)
d) CO₃^2-
e) none of the above

5. The reaction CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq) is exothermic.  Which of the following identifies the response of the reaction to an increase in temperature?
a) The reaction will shift to the left, so the pressure will increase.
b) The reaction will shift to the right, so the pressure will decrease.
c) Because the reaction involves liquids, there will be no effect.

6. What would happen in the reaction CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq) if the volume of the container is decreased?
a)  The pressure will increase, so the reaction will shift to the right, forming more 2H₃O⁺(aq) + CO₃^2- (aq)
b)  The pressure will increase, so the reaction will shift to the leftt, forming more CO₂ (g) + 3H₂O (l)
c)  The pressure will decrease, so the reaction will shift to the right, forming more 2H₃O⁺(aq) + CO₃^2- (aq)
d)  The pressure will decrease, so the reaction will shift to the left, forming more CO₂ (g) + 3H₂O (l)
  e) There will be no effect.

7. Which of the following substances would cause a common ion effect on the reaction CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq)? (Check all that apply)
a) Na₂CO₃      b) NaCl      c) CaCO₃      d) H₂SO₄

8.  HCl (hydrochloric acid) is a source of H₃O⁺(aq) ions.  Which of the following correctly describes the effect of adding some hydrochloric acid to a solution of carbon dioxide in water?

9. What would happen if some more N₂ were added to the container for the reaction CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq)?
a) The reaction would shift to the left.
b) The reaction would shift to the right.
c) There would be no change.

10.  The reaction: CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq) is important in describing how CO₂ (g) dissolves in water, such as the Earth's oceans.  Describe, using le Châtelier's principle, what you might expect to happen to the oceans' acidity over time as burning of fossil fuels increases the concentration of CO₂ (g) in the earth's atmosphere.

11. Suppose that more solid CaCO₃ is added to a beaker containing a saturated solution of calciuim carbonate.  What will the effect be after the solution is stirred?
a) The reaction would shift to the left.
b) The reaction would shift to the right.
c) There would be no change.

12. If some carbonate ions were added to this solution, then
a) The reaction would shift to the left.
b) The reaction would shift to the right.
c) There would be no change.

13. Solutions of Ca(OH)₂ (limewater) are used to test for the presence of carbon dioxide.  This test relies on the effect of le Châtelier's principle when two processes are combined:

• the solubility of CO₂ (g) in water: CO₂ (g) + 3H₂O (l) 2H₃O⁺(aq) + CO₃^2- (aq)
• the solubility of CaCO₃ in water: CaCO₃ (s) Ca²⁺ (aq) + CO₃^2- (aq)

Explain why dissolving CO₂ in limewater causes a cloudy precipitate to form.

14. The solubility equation for CaCO₃ (s) releases energy, so it can be written like this: CaCO₃ (s) Ca²⁺ (aq) + CO₃^2- (aq) + energy.  What would happen to the solubility of calcium carbonate as the temperature rises?
a) The solubility will increase.
b) The solubility will decrease.
c) There would be no change.