Le Chatelier’s Practice

1. What is the effect of an increase in pressure on each of the systems described by the following reactions?

2. During the industrial synthesis of methanol (CH3OH), carbon monoxide (CO) reacts with hydrogen gas. For methanol, ΔH= -100.4 kJ/mol.

  1. Write the balanced chemical equation for this reaction.
  2. Is it better to maintain this system at a low or high temperature, to obtain a good output?
  3. Is it preferable to maintain this system at high or low pressure? Explain.

3. The following phase change has reached equilibrium in a closed system:

  1. What is the effect of a reduction of volume by increasing the pressure?
  2. What is the effect of an increase in temperature?
  3. What is the effect of injecting some steam into the closed system, thus raising the pressure? Assume no temperature change.

4. Consider the system described by the following reaction:

What effect would the following changes have on the concentration of the substances at equilibrium? Use Le Châtelier's principle to support your answers.

  1. The temperature of the container used for the reaction decreases.
  2. The pressure increases.
  3. A catalyst is added.
  4. The volume of the container increases.
  5. [CO2] increases.

5. Using Le Châtelier's principle, explain what happens if Fe3+(aq) ions are added to the following reaction:

1. The following chemical equation represents the reaction between hydrogen and chlorine to form hydrogen chloride.

  1. List four important pieces of information conveyed by this equation.
  2. What are three important areas of interest concerning this reaction for which no information is indicated?

2. What is the effect on the equilibrium concentration of each substance in the system (increase, decrease or no change) when the listed reagents are added?

  1. H2(g) is added to the system described by:
  2. heat is added t to the system described by:
  3. CuSO4(g) is added to the system described by:
  4. Pb(NO3)2(s) is added to the system described by:
  5. AgCl(s) is added to the system described by:

3. The following equation represents one method for making methanol:

Predict the effect on the equilibrium concentrations of all substances if:

  1. the temperature is increased.
  2. the pressure is increased.

4. What would happen in each of the following systems at equilibrium if the total pressure is increased? The reactants and products are all gases.

  1. HI is formed from hydrogen and iodine
  2. H2S is formed by reacting hydrogen and sulphur

5. Consider the following system:

Which of the following choices will increase the quantity of C?

  1. adding a catalyst
  2. decreasing the [B]
  3. increasing the pressure
  4. increasing the temperature

6. Acetic acid dissociates according to the following equation.

Which of the following will occur if sodium acetate, NaCH3COO, is added to the solution?

  1. a precipitate will be formed
  2. more acetic acid will be ionized
  3. the concentration of hydrogen ions will decrease
  4. the solution will become more acidic