Chemistry Flashcards

Which type of bonding is present in sodium chloride (NaCl)?

Answer: Ionic bonding

NaCl is formed by the transfer of an electron from sodium to chlorine, creating an ionic bond between Na⁺ and Cl⁻ ions.

What is the oxidation state of sulfur in H₂SO₄?

Answer: +6

In H₂SO₄, hydrogen is +1 (×2 = +2) and oxygen is -2 (×4 = -8), so sulfur must be +6 to give an overall charge of zero.

A reaction has a negative ΔH and a negative ΔS. Under which condition is the reaction spontaneous?

Answer: At low temperatures only

When ΔH < 0 and ΔS < 0, ΔG = ΔH – TΔS is negative (spontaneous) only at low temperatures where the enthalpy term dominates.

Which of the following is an example of a nucleophilic substitution reaction?

Answer: Reaction of bromoethane with KOH(aq)

OH⁻ acts as a nucleophile attacking the carbon bonded to Br in bromoethane, replacing Br in an SN2-type substitution.

What does Le Chatelier's principle predict when pressure is increased on the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g)?

Answer: Equilibrium shifts right, producing more NH₃

Increasing pressure shifts equilibrium toward the side with fewer moles of gas; the right side has 2 moles vs. 4 on the left, so more NH₃ is produced.

Which property best distinguishes a strong acid from a weak acid of the same concentration?

Answer: Degree of ionisation

A strong acid fully ionises in water (degree ≈ 100%), while a weak acid only partially ionises, resulting in a lower H⁺ concentration.

In an electrochemical cell, oxidation occurs at the:

Answer: Anode

Oxidation is the loss of electrons, and this always occurs at the anode of an electrochemical cell.