Units 3 & 4 Multiple Choice Questions #1

Which of the following is the correct equilibrium expression for the reaction below? Fe₂O₃(s) + 3CO(g) ⇌ 2Fe(s) + 3CO₂(g)

• [CO₂]³ / [CO]³

• [CO₂]³ / [Fe₂O₃][CO]³

• [Fe₂O₃][CO]³ / [Fe]²[CO]³

• [Fe]²[CO₂]³ / [Fe₂O₃][CO]³

Answer explanation

The equilibrium expression is derived from the products and reactants. Solids (Fe₂O₃ and Fe) do not appear in the expression. Thus, the correct expression is [CO₂]³ / [CO]³, focusing only on the gaseous components.

Consider the two reactions at equilibrium shown below.

2NO₂(g) ⇌ N₂O₄(s) ΔH = - 60 kJ mol⁻¹

N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = - 92 kJ mol⁻¹

Which action will drive BOTH reactions to form more product?

• reducing the pressure

• increasing the reaction temperature

• increasing the volume of the reaction vessel

• removing the product from the reaction vessel

Answer explanation

Removing the product shifts the equilibrium to the right for both reactions, favoring product formation. For 2NO₂ ⇌ N₂O₄ and N₂ + 3H₂ ⇌ 2NH₃, this action increases the concentration of reactants, driving both reactions forward.

The table shows the colours of three indicators as the hydrogen ion concentration changes.

Which statement about the solution is correct?

• The solution is weakly acidic with a pH of 6.

• The solution is strongly acidic with a pH of 6.

• The solution is weakly alkaline with a pH of 8.

• The solution is strongly alkaline with a pH of 8.

Answer explanation

A pH of 6 indicates a weakly acidic solution, as it is below 7 but not low enough to be considered strongly acidic. Therefore, the correct statement is that the solution is weakly acidic with a pH of 6.

Which statement about this titration is correct?

• The acid was placed in the burette and the equivalence point occurred at pH 7.

• The base was placed in the burette and the equivalence point occurred at pH 12.

• The acid was placed in the conical flask and the equivalence point occurred at pH 7.

• The acid was placed in the conical flask and the equivalence point occurred at pH 12.

Answer explanation

In a typical acid-base titration, if the acid is in the conical flask and a strong base is in the burette, the equivalence point is at pH 7, indicating neutralization. Thus, the correct statement is that the acid was in the flask and pH 7 was reached.

Calculate the concentration of H⁺ ions in solution if the [OH⁻] = 1.8 x 10⁻⁹ M.

• 3.56 x 10⁻⁶ M

• 4.56 x 10⁻⁶ M

• 5.56 x 10⁻⁶ M

• 6.56 x 10⁻⁶ M

A protein is formed when:

• amino acids are joined by peptide bonds.

• amino acids are joined by glycosidic bonds.

• glucose molecules are joined by peptide bonds.

• glucose molecules are joined by glycosidic bonds.

Consider the following reaction: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g) Which statement is correct?

• H₂ is reduced.

• Cl^- is reduced.

• Mg is oxidised.

• Mg is reduced.

Deduce the oxidation number of Mn in K₂MnO₄.

• +2

• +4

• +5

• +6

The table lists some boiling point temperatures of a range of organic molecules. What is the main reason why carboxylic acids have a higher boiling point than alcohols?

• Alcohols have a higher molecular weight than carboxylic acids.

• Carboxylic acids form strong dispersion forces between molecules.

• Carboxylic acids have strong ionic bonds between the acid molecules.

• Carboxylic acids have stronger hydrogen bonding compared to alcohols.

Identify which of the compounds shown below would produce the following IR spectrum.

• hexane

• 1-hexanol

• 3-hexanone

• 2-methylhexanal