Higher Chemistry - Equilibrium & Chemical Analysis Test Revision

Which of the following statements regarding a chemical reaction at equilibrium is always correct?

• The rates of the forward and reverse reactions are equal.

• The concentration of reactants and products are equal.

• The forward and reverse reactions have stopped

• The addition of a catalyst changes the position of the equilibrium.

Which line in the table best describes the effect of adding a catalyst to the following reaction?

4NH₃(g) + 5O₂(g) ⇌ 4NO(g) + 6H₂O(g) ΔH = −ve

• A

• B

• C

• D

Consider the following reaction:

4NH₃(g) + 5O₂(g) ⇌ 4NO(g) + 6H₂O(g) ΔH = −ve

What would happen to the position of equilibrium if the temperature was increased?

• moves to left

• moves to right

• is unchanged

• moves to right and then left

Cl₂(g) + H₂O(ℓ) ⇌ Cl⁻ (aq) + ClO⁻ (aq) + 2H⁺ (aq )

The addition of which of the following substances would move the above equilibrium to the right?

• Hydrogen

• Hydrogen chloride

• Sodium chloride

• Sodium hydroxide

ICl(ℓ) + Cl₂(g) ⇌ ICl₃(s) ΔH = −106 kJ mol⁻¹

Which line in the table identifies correctly the changes that will cause the greatest increase in the proportion of solid in the above equilibrium mixture?

• A

• B

• C

• D

In which of the reactions shown would the yield of product be increased by lowering the pressure?

• A

• B

• C

• D

In a reversible reaction, equilibrium is reached when

• molecules of reactants cease to change into molecules of products

• the concentrations of reactants and products are equal

• the concentrations of reactants and products are constant

• the activation energy of the forward reaction is equal to that of the reverse reaction.

A student was carrying out a titration to establish the concentration of vitamin C using iodine solution. Which of the following would help the student achieve a precise end-point?

• Placing a white tile underneath the conical flask

• Using the bottom of the meniscus when reading the burette

• Repeating titrations

• Carrying out a rough titration first

The vitamin C content of a carton of orange juice was determined by four students. Each student carried out the experiment three times.

The most reproducible results were obtained by

• Student A

• Student B

• Student C

• Student D

Aluminium carbonate can be produced by the following reaction.

2AlCl₃ (aq)     +          3K₂CO₃ (aq)          →      Al₂(CO₃)₃ (s)      +       6KCl (aq)

The most suitable method of obtaining a sample of the aluminium carbonate is

• collection over water

• distillation

• filtration

• evaporation