WASSCE SHS
An acid turns blue litmus red and has a pH below 7. Its reactions with metals, bases and carbonates are predictable, and each one names a salt.
Dilute acids react with reactive metals such as zinc to give a salt and hydrogen. The hydrogen pops with a lighted splint. They react with bases to give a salt and water only. That is neutralisation. They react with carbonates to give a salt, water and carbon dioxide, and the carbon dioxide turns limewater milky. The salt takes its first name from the metal and its second name from the acid. Hydrochloric acid gives chlorides, sulphuric acid gives sulphates, and nitric acid gives nitrates.
A base that dissolves in water is an alkali and has a pH above 7. pH 7 is neutral. Indicators are dyes that change colour with pH. Litmus is enough for acid or alkali. A universal indicator gives a colour along the scale and so an approximate pH. In the laboratory you do not taste acids, even though textbooks say acids taste sour. That description belongs to safe household examples. Concentrated acids are corrosive. The questions on this page are about dilute acids.
Name the gas and the test. Hydrogen pops. Carbon dioxide turns limewater milky. Oxygen relights a glowing splint, and it is not a product of these three reactions. The salt must match both parents of the reaction. Zinc and hydrochloric acid give zinc chloride, not zinc sulphate. Show states only if the question asks for a symbol equation. A word equation is enough unless symbols are required.
These are practice questions in the style of the paper, with a model answer and a mark scheme. They are not a promise of what your paper will ask.
4 marks
Dilute hydrochloric acid is added to zinc granules.
(a) Name the gas produced. (1 mark)
(b) State the test for the gas and the result. (2 marks)
(c) Name the salt left in solution. (1 mark)
(a) Hydrogen.
(b) A lighted splint at the mouth of the tube gives a pop.
(c) Zinc chloride.
3 marks
Write the word equation for the reaction of sodium hydroxide with dilute hydrochloric acid, and state the type of reaction. (3 marks)
Sodium hydroxide + hydrochloric acid → sodium chloride + water. The reaction is neutralisation.
2 marks
A white solid fizzes when dilute acid is added, and the gas turns limewater milky. What ion or type of compound does the solid contain? Name the gas. (2 marks)
The solid is a carbonate, or it contains the carbonate ion. The gas is carbon dioxide.
More questions on this topic are inside GLearn, marked as you answer, with the reason written out. The first ones need no account.
Practise Integrated Science freeHydrochloric acid forms chlorides, sulphuric acid forms sulphates, and nitric acid forms nitrates. The metal in the name comes from the metal, the base or the carbonate you started with. Zinc with hydrochloric acid gives zinc chloride.
A lighted splint pops in hydrogen. Do not confuse it with oxygen, which relights a glowing splint, or with carbon dioxide, which turns limewater milky. All WASSCE Integrated Science past questions