Chapter 2 – Summary

Review

Try the following review questions to check your understanding of the concepts in this chapter.

1. Which of the following properties could not be used to tell if a chemical reaction is at equilibrium?

a) constant color intensity
b) constant gas pressure
c) constant concentration		 d) constant electrical conductivity
e) constant mass
f) all of them could be used

Potassium dichromate2. The color intensity of a solution of potassium dichromate (there is still some solid at the bottom of the beaker) does not appear to change after a few minutes of stirring.   Which of the following statements is correct?
  a) The solution is at equilibrium, since it has unchanging properties.
  b) The system might be at equilibrium; however, it may be that the potassium dichromate will dissolve more if it is given more time.
  c) Equilibrium does not apply to this solution.
  d) The system is at equilibrium; however, if we stirred it harder so that more solid potassium dichromate dissolved, then the system would reach a new equilibrium.

3. In the reaction H2 (g) + I2 (g) 2 HI (g), which of the following conditions would eventually reach equilibrium?
  a) adding some H2 and I2 to a sealed container.
  b) adding just some HI to a sealed container.
  c) adding some H2 and HI, but no I2 to a sealed container.
  d) adding just some H2 to a sealed container.

4. What is equal in an equilibrium reaction?
  a) the products and reactants.
  b) the concentrations of products and reactants.		   c) the forward and reverse reaction rates.
  d) all of the above.

5. Why will the following reaction not become an equilibrium, if the calcium carbonate (limestone) is heated in the open air?

CaCO3 (s) CaO (s) + CO2 (g)

  a) because some of the materials are solids, and some are gases
  b) the oxygen from the air will react, but has not been included in the equation.
  c) because the equation is not balanced.
  d) because the system is open, not closed.

6. The balanced equation CO (g) + NO2 (g) CO2 (g) + NO (g) indicates that there will be equal quantities of reactants and products at equilibrium, since all the coefficients are the same.
  True       False

7. If you started with an empty container, and put in 1 mole of CO (g) and 2 moles of NO2 (g) and let it react according to this equation:

CO (g) + NO2 (g) CO2 (g) + NO (g)

then when the reaction reached an equilibrium you know that:
  a) the amount of CO2 (g)  will equal the amount of NO (g), but they won't necessarily be the same as the amount of CO(g)  and  NO2(g).
  b) the amount of CO2 (g)  will equal the 1/2 of the amount of NO (g).
  c) the amount of CO2 (g)  will equal 2 times the amount of NO (g).
  d) the amounts of all four molecules will be the same, since all the coefficients are 1. 

8. Heavy water contains deuterium atoms in place of the hydrogen in normal water.   How could you use water enriched with deuterium (D2O) to prove that

H2O (l) H2O (g)

is a dynamic equilibrium?  Write out an answer, then click this button to check your answer.