Higher Chemistry Unit 3 MCQ Revision

A reaction has the potential energy diagram shown

The activation energy for the forward reaction is

• X –Y

• Y –X

• Y –Z

• Z –Y.

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.

Consider the reaction pathway shown.

According to Hess’s Law, the ΔH value, in kJ mol⁻¹ , for reaction Z to Y is

• +74

• -74

• +346

• -346

The diagram shows the energy profiles for a reaction carried out with and without a catalyst. What is the enthalpy change, in kJ mol^–1, for the catalysed reaction?

• -100

• -50

• +50

• +100

The mean bond enthalpy of a C – F bond is 484 kJ mol⁻¹ . In which of the processes is ΔH approximately equal to +1936 kJ mol⁻¹ ?

• CF₄(g) → C(s) + 2F₂(g)

• CF₄(g) → C(g) + 4F(g)

• CF₄(g) → C(g) + 2F₂(g)

• CF₄(g) → C(s) + 4F(g)

Which of the following equations represents the enthalpy of combustion of propane?

• C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(ℓ)

• C₃H₈(g) + 3.5O₂(g) → 3CO(g) + 4H₂O(ℓ)

• C₃H₈(g) + 3O₂(g) → 3CO₂(g) + 4H₂(g)

• C₃H₈(g) + 1.5O₂(g) → 3CO(g) + 4H₂(g)

xP₂H₄ + yO₂ → P₄O₁₀ + zH₂O

The equation is balanced when

• x = 1, y = 5, z = 4

• x = 4, y = 6, z = 2

• x = 2, y = 7, z = 4

• x = 2, y = 5, z = 2

The atom economy for the production of titanium in the equation shown is equal to

• 
• 
• 
• 

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

Bromine and hydrogen react together to form hydrogen bromide

H₂(g) + Br₂(g) → 2HBr(g)

• -102

• +102

• -264

• +264