Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.

Lesson: Le Chatelier's Principle

Worksheet • 18 Questions

Q1:

A suspension contains solid M g ( O H ) 2 in equilibrium with dissolved M g 2 + and O H ions. If solid K O H is added to the suspension, which of the following effects is not observed?

  • A [ O H ] decreases.
  • BThe pH increases.
  • CThe amount of solid M g ( O H ) 2 increases.
  • D [ K ] + increases.
  • E [ M g ] 2 + decreases.

Q2:

A suspension contains solid M g ( O H ) 2 in equilibrium with dissolved M g 2 + and O H ions. If solid M g C l 2 is added to the suspension, which of the following effects is not observed?

  • A [ O H ] increases.
  • BThe pH decreases.
  • C [ M g ] 2 + increases.
  • D [ C l ] increases.
  • EThe amount of solid M g ( O H ) 2 increases.

Q3:

A suspension contains solid N i C O 3 in equilibrium with dissolved [ N i ] 2 + and C O 3 2 ions. If solid K C O 2 3 is added to the suspension, which of the following effects is not observed?

  • A [ N i ] 2 + stays constant.
  • BThe pH increases.
  • CThe amount of solid N i C O 3 increases.
  • D [ K ] + increases.
  • E [ C O ] 3 2 increases.

Q4:

A suspension contains solid N i C O 3 in equilibrium with N i 2 + and C O 3 2 ions. If solid N i ( N O ) 3 2 is added to the solution, which of the following effects is not observed?

  • AThe solubility of solid N i C O 3 increases.
  • B [ N O ] 3 increases.
  • CThe amount of solid N i C O 3 increases.
  • D [ C O ] 3 2 decreases.
  • E [ N i ] 2 + increases.

Q5:

A suspension contains solid M g ( O H ) 2 in equilibrium with dissolved M g 2 + and O H ions. If more solid M g ( O H ) 2 is added to the suspension, which of the following effects is not observed?

  • A [ O H ] increases.
  • BThe amount of H O 2 stays constant.
  • CThe addition of solid M g ( O H ) 2 has no effect on the equilibrium.
  • D [ M g ] + stays constant.
  • EThe amount of solid M g ( O H ) 2 increases.

Q6:

A suspension contains solid M g ( O H ) 2 in equilibrium with dissolved M g 2 + and O H ions. If an acid is added to the suspension, which of the following effects is not observed?

  • A [ M g ] 2 + remains constant.
  • BThe amount of H O 2 increases.
  • CThe amount of solid M g ( O H ) 2 decreases.
  • D [ O H ] decreases.
  • E [ H ] + increases.

Q7:

A suspension contains solid A g C r O 2 4 in equilibrium with a saturated solution of A g + and C r O 4 2 ions. If 99 g of solid A g C r O 2 4 is added to the suspension, how are the concentrations of A g + and C r O 4 2 affected?

  • A [ A g ] + and [ C r O ] 4 2 both remain constant.
  • B [ A g ] + increases by a factor of 200 and [ C r O ] 4 2 increases by a factor of 100.
  • C [ A g ] + and [ C r O ] 4 2 both increase by a factor of 100.
  • D [ A g ] + increases by a factor of 50 and [ C r O ] 4 2 increases by a factor of 100.
  • E [ A g ] + increases by a factor of 100 and [ C r O ] 4 2 increases by a factor of 50.

Q8:

Solutes A and B react to produce solutes C and D in a reversible reaction, as shown by the equation. In a solution at equilibrium, the concentrations of A , B , C , and D are [ A ] , [ B ] , [ C ] , and [ D ] respectively. When a small quantity of compound C 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?

  • A The position of equilibrium moves to the left to lower [ C ] .
  • B The position of equilibrium is unchanged as the reaction has no effect on the number of solute molecules.
  • C The position of equilibrium moves to the right to lower [ C ] .
  • D The position of equilibrium moves to the right to raise [ C ] .
  • E The position of equilibrium moves to the left to raise [ C ] .

Which equilibrium concentrations increase when compound C is added?

  • A [ A ] , [ B ] , and [ C ] only
  • B [ C ] only
  • C [ A ] , [ B ] , [ C ] , and [ D ]
  • D [ A ] and [ B ] only
  • E [ C ] and [ D ] only

Which of the following ratios of equilibrium concentrations does not change when compound C is added?

  • A [ A ] [ B ]
  • B [ A ] [ C ]
  • C [ B ] [ D ]
  • D [ C ] [ D ]

Q9:

In which of the following reactions would the addition of hydrochloric acid decrease the quantity of solid material?

  • A B i C l ( ) + H O ( ) B i O C l ( ) + 2 H C l ( ) 3 2 a q l s a q
  • B [ C u ( H O ) ] ( ) + 4 C l ( ) [ C u C l ] ( ) + 6 H O ( ) 2 6 2 + 4 2 2 a q a q a q a q
  • C N H C l ( ) N H ( ) + H C l ( ) 4 3 s a q a q
  • D [ C r ( H O ) ( O H ) ] ( ) + 3 O H ( ) [ C r ( O H ) ] ( ) + 3 H O ( ) 2 3 3 6 3 2 s a q a q l
  • E A g N O ( ) + C l ( ) A g C l ( ) + N O ( ) 3 3 a q a q s a q

Q10:

In which of the following gas-phase reactions would the equilibrium yield increase with increasing pressure?

  • A 2 N O + C H O H C H O N O + H N O 2 3 3 3
  • B S C l + C l 2 S C l 2 2 2 2
  • C C H + H O C O + 3 H 4 2 2
  • D O F + S O S O + F 2 2 3 2
  • E P C l P C l + C l 5 3 2

Q11:

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 +206 kJ/mol.

Which of the following changes would produce the greatest increase in the yield of hydrogen?

  • AIncreasing temperature and decreasing pressure
  • BDecreasing pressure at constant temperature
  • CIncreasing both temperature and pressure
  • DIncreasing temperature at constant pressure
  • EDecreasing both temperature and pressure

Which of the following graphs best represents the change in equilibrium yield as the reaction temperature decreases below 1 0 0 C at 1 atm pressure?

  • A
  • B
  • C
  • D
  • E

Q12:

Gaseous phosphorus pentachloride ( P C l ) 5 decomposes into phosphorus trichloride ( P C l ) 3 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?

  • A
  • B
  • C
  • D
  • E

Which diagram represents the rates of the forward and backward reactions when the pressure is decreased at constant temperature?

  • A
  • B
  • C
  • D
  • E

Q13:

The colorless gas dinitrogen tetroxide ( N O ) 2 4 decomposes reversibly into the brown gas nitrogen dioxide ( N O ) 2 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 syringe contains a larger number of gas molecules.
  • BThe pressure of the gas in the syringe is higher.
  • CThe syringe contains a larger mass of gas molecules.
  • DThe temperature of the gas in the syringe is higher.
  • EThe syringe contains gas molecules with a larger average size.

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?

  • A
  • B