National Examinations Council
NECO Chemistry · Paper I — Practical
Sat on a separate day from the written papers.
8 exam-style questions, written to the National Examinations Council format and free to read. The answers are here too — what they do not tell you is how many you would get right with a clock running.
1. The solubility of a salt was determined at 30 °C by evaporating 25 cm³ of its saturated solution to dryness, leaving 4.5 g of solid.
(a) Calculate the solubility in g per 100 g of water, assuming the density of the solution is 1 g/cm³. [8 marks]
(b) Describe how the saturated solution should be prepared. [8 marks]
(c) State one source of error in this method. [4 marks]
2. A portion of specimen Q is treated with dilute trioxonitrate(V) acid followed by silver trioxonitrate(V) solution. A white precipitate forms which dissolves in aqueous ammonia.
(a) State the observation and the inference. [8 marks]
(b) Write the ionic equation for the precipitation. [6 marks]
(c) State why the acid is added before the silver salt. [6 marks]
3. Specimen U is a colourless liquid that decolourises bromine water.
(a) State the observation and the inference. [6 marks]
(b) Name the class of compound to which U belongs and give one example. [6 marks]
(c) Describe one further test that would distinguish U from an alkane. [8 marks]
4. A hydrated salt was heated to constant mass. Mass of crucible plus hydrated salt was 24.80 g; after heating it was 22.40 g; the empty crucible was 18.00 g.
(a) Calculate the mass of water lost and the mass of anhydrous salt. [8 marks]
(b) Explain what is meant by heating to constant mass. [6 marks]
(c) State two precautions in this experiment. [6 marks]
5. Specimen P is dissolved in water and aqueous ammonia is added drop by drop until in excess. A pale blue precipitate forms which dissolves to a deep blue solution.
(a) State the observation at each stage. [6 marks]
(b) State the inference drawn from each observation. [8 marks]
(c) Describe one confirmatory test for the cation identified. [6 marks]
Reading these is not the same as sitting them.
Every question above is answerable given time. The exam does not give you time. Sit the whole paper on the real clock and the number you get back is the one that means something.
Sit it against the clock — freeExampaper is an independent study service. It is not affiliated with, endorsed by, or connected to WAEC, NECO, JAMB or any examination body. Exam names and subject titles are used only to describe what each paper is for.