ENERGY CHANGE AND ACIDS & BASES

The chemical equation that represents an endothermic reaction:

• NH₄NO₃(s) + H₂O(ℓ) → NH₄⁺(aq) + NO₃^-(aq) ΔH > 0

• 2Mg(s) + O₂(g) → 2MgO(s) ΔH < 0

• Zn(s) + 2HCℓ(aq) → ZnCℓ₂(aq) + H₂(g) + heat

• H₂(g) + Cℓ₂(g) → 2HCℓ(g) ΔH = -131 kJ∙mol^-1

The CORRECT formula for nitric acid:

• H₂SO₄

• CH₃COOH

• NH₃

• HNO₃

Which ONE of the reactions below will produce the salt sodium ethanoate (sodium acetate)?

• HCℓ(s) + CH₃COOH(aq) →

• CH₃COOH(aq) + H₂O(ℓ) →

• CH₃COOH(aq) + NaOH(aq) →

• H₂CO₃(aq) + NaOH(aq) →

According to the Arrhenius theory, all bases …

• are proton donors.

• are proton acceptors.

• form H₃O⁺ ions in solution.

• form OH^- ions in solution.

Which ONE of the following is NOT a typical reaction of hydrochloric acid?

• It neutralises a base with the release of hydrogen gas.

• It forms hydronium ions in water.

• It colours lithmus paper red.

• It forms CO₂ when reacting with a metal carbonate.

Which ONE of the following pairs represents the conjugate acid and conjugate base of HPO₄^2- ?

• A

• B

• C

• D

Which ONE of the following indicates the CORRECT colour of bromothymol blue in an acid and a base?

• A

• B

• C

• D

• HCO₃^- (aq) and OH^- (aq)

• H2O(ℓ) and OH^- (aq)

• H2O(ℓ) and HCO₃^- (aq)

• OH^- (aq) and CO₃^2-(aq)

A few drops of bromothymol blue indicator are added to a hydrochloric acid solution, HCℓ(aq). When ammonium hydroxide, NH₄OH(aq), is added to this solution, the colour of the indicator will change from …

• blue to yellow.

• yellow to blue.

• yellow to red.

• blue to red.

The diagram shows the energy profile for a reaction that occurs with and without a catalyst

Which one of the following can be deduced from the diagram?

• 2 is the activation energy of the reverse catalysed reaction.

• The forward catalysed reaction is endothermic.

• The enthalpy change of the reaction is (4 – 1)

• The enthalpy change of the reaction is decreased by using a catalyst