Worksheet: Le Chatelier's Principle
In this worksheet, we will practice using energy changes and stoichiometry to predict the effects of temperature and pressure on equilibrium yields.
A suspension contains solid in equilibrium with dissolved and ions. If more solid is added to the suspension, which of the following effects is not observed?
- A increases.
- B stays constant.
- CThe addition of solid has no effect on the equilibrium.
- DThe amount of solid increases.
- EThe amount of stays constant.
A suspension contains solid in equilibrium with a saturated solution of and ions. If 99 g of solid is added to the suspension, how are the concentrations of and affected?
- A increases by a factor of 50 and increases by a factor of 100.
- B increases by a factor of 100 and increases by a factor of 50.
- C and both remain constant.
- D increases by a factor of 200 and increases by a factor of 100.
- E and both increase by a factor of 100.
Solutes and react to produce solutes and in a reversible reaction, as shown by the equation. In a solution at equilibrium, the concentrations of , , , and are , , , and respectively. When a small quantity of compound is added to this solution, the composition of the solution changes according to Le Chatelier’s principle.
According to Le Chatelier’s principle, how and why does the position of equilibrium change?
- AThe position of equilibrium moves to the right to lower .
- BThe position of equilibrium moves to the left to raise .
- CThe position of equilibrium is unchanged as the reaction has no effect on the number of solute molecules.
- DThe position of equilibrium moves to the left to lower .
- EThe position of equilibrium moves to the right to raise .
Which equilibrium concentrations increase when compound is added?
- A , , , and
- B , , and only
- C and only
- D only
- E and only
Which of the following ratios of equilibrium concentrations does not change when compound is added?
In which of the following reactions would the addition of hydrochloric acid decrease the quantity of solid material?
Methane reacts with steam in the presence of a catalyst to produce carbon monoxide and hydrogen gases, as shown in the equation:
The enthalpy change for this reaction is kJ/mol.
Which of the following changes would produce the greatest increase in the yield of hydrogen?
- AIncreasing temperature at constant pressure
- BDecreasing both temperature and pressure
- CIncreasing temperature and decreasing pressure
- DIncreasing both temperature and pressure
- EDecreasing pressure at constant temperature
Which of the following graphs best represents the change in equilibrium yield as the reaction temperature decreases below at 1 atm pressure?
Gaseous phosphorus pentachloride decomposes into phosphorus trichloride and chlorine gases, as shown in the equation:
The enthalpy change for this reaction is +87.9 kJ/mol. The rates of the forward and backward reactions are shown schematically in the diagram:
Which diagram represents the rates of the forward and backward reactions when the temperature is increased at constant pressure?
Which diagram represents the rates of the forward and backward reactions when the pressure is decreased at constant temperature?
The colorless gas dinitrogen tetroxide decomposes reversibly into the brown gas nitrogen dioxide with a reaction enthalpy of +57.2 kJ/mol: A student stores a sample of dinitrogen tetroxide in a gas syringe at room temperature and 1 atm pressure and allows the plunger of the syringe to move freely. The gas is left to decompose until equilibrium is reached, as shown.
Why is the position of the plunger at equilibrium different from its position at the start of the reaction?
- AThe pressure of the gas in the syringe is higher.
- BThe syringe contains gas molecules with a larger average size.
- CThe temperature of the gas in the syringe is higher.
- DThe syringe contains a larger number of gas molecules.
- EThe syringe contains a larger mass of gas molecules.
The student heats the gas syringe and allows the plunger of the syringe to move freely. Which diagram best illustrates the gas syringe under the new reaction conditions once equilibrium has been reached?