WAEC SNIPPETS # 1

Compiled from WAEC Chemistry past questions

By Kingsley Idiagbor, B.Sc. (Hons), NCE, PGDCs, MNSM

1. 50cm³ of sulphur (IV) oxide were produced at s.t.p. when same quantity of powdered sulphur were burnt in excess oxygen. (a) Write the equation for the equation;
   (b) Calculate the volume of oxygen used up during the reaction;
   (c) Which of the gas laws is applicable?
   State the law. [WAEC June 1988]
2. (a) When is a sample of water said to be hard? (b) State one difference between temporary and permanent hardness of water;
   (c) Give one method of removing hardness completely from water;
   (d) Name two local materials used for the production of soap [WAEC Nov 1989]
3. (a) Write the electronic configuration of an element with atomic number 15 indicating the distribution of electrons in the energy sub-levels;
   (b) Give the formula and the colour of the complex formed between ammonia and copper (II) ions [WAEC Nov 1990]
4. (a) State one method of collecting gases which are denser than air;
   (b) Name two gases that can be used to perform the fountain experiment in the laboratory; State the physical property which makes them suitable for the experiment. [WAEC 1992]
5. (a) (i) List four characteristics of transition metals; (ii)Name two metals that can be extracted from their ore by electrolysis
   (b) (i) Determine the oxidation number of chromium in Cr₂O₇^2-
   (ii) State the colour observed on adding a few drops of dilute tetraoxosulphate (VI) acid to the system represented by the following equation:
   (c) (i) State and explain what would be observed if hydrogen sulphide gas were bubbled into acidified K₂Cr₂O₇. Write an equation for the equation (ii) What precaution should be taken to avoid excessive exposure to hydrogen sulphide gas while it is being generated in the laboratory? [WAEC 1993]

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