Methanoic acid, HCO2H, and hydrocyanic acid, HCN, can both behave as acids. A solution of methanoic acid has a lower pH than a solution of hydrocyanic acid of the same concentration. Which statements explain this? 1 HCO2H molecules dissociate more fully than HCN molecules do. 2 Each HCO2H molecule has two hydrogen atoms; each HCN molecule only has one. 3 Methanoic acid is a weaker acid than hydrocyanic acid.

Sulfur dioxide and oxygen react in the gas phase. 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) ∆H = –197 kJ mol⁻¹ Which statements are c…

The reaction between sulfur dioxide and oxygen is reversible. 2SO₂ + O₂ ⇌ 2SO₃ ΔH° = –196 kJ mol⁻¹ Which conditions o…

In which reactions does NH₃ behave as a Brønsted-Lowry acid? 1 2NH₃ → NH₂⁻ + NH₄⁺ 2 HSO₄⁻ + NH₃ → SO₄²⁻ + NH₄⁺ 3 Ag⁺ …

For the element sulfur, which pair of ionisation energies has the largest difference between them?

Which ion has both more electrons than protons and more protons than neutrons? [H = ¹H; D = ²H; O = ¹⁶O]

Which species contains the smallest number of electrons?