Chemistry Flashcards

What is the pH of a 0.01 mol/dm³ solution of hydrochloric acid?

Answer: 2

HCl is a strong acid that fully dissociates: [H⁺] = 0.01 = 10⁻² mol/dm³. pH = -log₁₀[H⁺] = -log₁₀(10⁻²) = 2.

What is the test for an aldehyde using Tollens' reagent?

Answer: A silver mirror forms on the test tube walls

Tollens' reagent (ammoniacal silver nitrate) is reduced by aldehydes to form metallic silver, which deposits as a mirror-like coating on the test tube. This is the 'silver mirror test'.

What is the molecular geometry of SF₆ according to VSEPR theory?

Answer: Octahedral

SF₆ has six bonding pairs around the central sulphur atom and no lone pairs, giving an octahedral geometry with 90° bond angles.

In electrochemistry, what happens at the cathode during electrolysis?

Answer: Reduction occurs — cations gain electrons

At the cathode (negative electrode), cations are attracted and gain electrons (reduction). Remember: 'CATions go to the CAThode' and 'Reduction at the Cathode'.

What is a peptide bond in the context of A-Level organic chemistry?

Answer: A covalent bond formed between the amino group of one amino acid and the carboxyl group of another through a condensation reaction

A peptide bond (-CO-NH-) forms through a condensation reaction between the -NH₂ group of one amino acid and the -COOH group of another, releasing a molecule of water.

What is the first ionisation energy trend across Period 3 of the Periodic Table?

Answer: It generally increases across the period with dips at Al and S due to electron configuration effects

First ionisation energy generally increases across Period 3 due to increasing nuclear charge. However, dips occur at Al (electron enters 3p, easier to remove) and S (paired electron in 3p experiences repulsion).