2017 WAEC GCE Chemistry Practical Specimen Questions is Out.
The West African Examination Council (WAEC) General Certificate Examination (GCE) for November/December Waec Chemistry alternative to practical paper will be written on Friday, 15th September, 2017 from 9:30am to 11:00am.
WAEC GCE Chemistry Practical Specimen 2017:
Paper 3 (Alternative To Practical) Answer Three questions. Write your answers in the spaces provided.
1. A student adds a known mass of magnesium ribbon to 100 cm3 of dilute hydrochloric acid (an excess) in the apparatus shown below. Hydrogen gas is evolved. The time taken to collect 48 cm3 of gas at room temperature and pressure is measured.
(a) (i) Name apparatus A. (ii) Name apparatus B. (b) (i) Calculate the number of moles of hydrogen in the 48 cm3 of gas. [1 mole of any gas occupies 24 000 cm3 at room temperature and pressure.]
(ii) Use the equation below to deduce the mass of magnesium used in the experiment to produce 48 cm3 of hydrogen at room temperature and pressure. [Ar : Mg, 24] Mg + 2HCl MgCl2 + H2 (c) Give a test for hydrogen gas.
(d) What is the effect on the time taken to collect the same volume of gas if, (i) large lumps of the same mass of magnesium are used instead of magnesium ribbon, (ii) the reaction is carried out at a higher temperature?
2. (a) A student investigates the electrolysis of aqueous copper(II) sulfate using graphite electrodes and the apparatus shown below.
(i) What is observed at electrode R? (ii) Construct the equation for the reaction taking place at electrode R. (iii) When graphite electrodes are used a colour change is seen in the solution. What is this colour change? Explain why it happens. (iv) When graphite electrodes are used, a gas is evolved at one of the electrodes. Name the gas and give a test for the gas. (v) If the graphite electrodes are replaced with copper electrodes, no colour change is seen on electrolysis of the solution. Explain why.
(b) The student does more experiments using the apparatus in (a) with graphite electrodes but, in each case, using a different electrolyte. Complete the table below.