GCSE Chemistry: Acids, Bases and Salts

Acids and bases give GCSE Chemistry its most pattern-rich topic: four general reaction equations that, once learned, let you predict the products of dozens of specific reactions. This quiz tests the patterns and the understanding behind them.

The pH scale opens the set with the fact most students miss: the scale is logarithmic, so each unit represents a tenfold change in hydrogen ion concentration. The general reactions then take over: acid plus metal giving salt and hydrogen (with a question on which substances actually produce the gas — position in the reactivity series matters), acid plus metal oxide and acid plus metal hydroxide giving salt and water, and acid plus metal carbonate giving all three products — salt, water and carbon dioxide, tested as a three-answer multi-select.

Salt naming runs through the set: magnesium sulfate from sulfuric acid, potassium nitrate from nitric acid — the acid-to-salt-name mapping (chloride, sulfate, nitrate) that costs easy marks when misremembered. The practical dimension appears through the standard preparation of a pure soluble salt: why the insoluble base is added in excess (to guarantee all the acid reacts) before filtering and crystallising.

The Higher tier material addresses the distinction examiners love: strong versus weak (degree of ionisation) as opposed to concentrated versus dilute (amount per volume) — two separate axes that students routinely conflate — plus the characteristics of weak acids, including their higher pH at equal concentration.

Every question is self-contained, and each explanation restates the general equation being applied, reinforcing the pattern-recognition skill the whole topic is built on.

• Interpret the logarithmic pH scale
• Predict products of acids reacting with metals, oxides, hydroxides and carbonates
• Name the salts formed by hydrochloric, sulfuric and nitric acids
• Describe the preparation of a pure soluble salt using an excess of insoluble base
• Distinguish strong from weak acids and separate that axis from concentration (Higher)

Topic scope follows the Department for Education's GCSE combined science subject content, chemical changes strand: pH and neutralisation, reactions of acids, salt preparation, and strong versus weak acids.