Waec Chemistry 2014 Past Questions and Answers

Question 46:

• WAEC 2014

The oxide from electric power station is

A. Carbon (IV) oxide
B. Copper (ll) oxide
C. Nitrogen (IV) oxide
D. Sulphur (IV) oxide

Question 47:

• WAEC 2014

(a)(i) Define ionic bond.
(ii) What type of bond (s) exist (s) in: I. magnesium oxide; II. ammonium ion?

(b) Determine the oxidation number of sulphur in Na\(_2\)S\(_2\)O\(_2\).

(c) State Faraday's first law.

(d) Give one example each of: (i) acid salt; (ii) base salt.

(e) Name the type of energy change that occurs in each of the following processes
(i) I\(_{2(s)}\) \(\to\) I\(_{2(g)}\)
(ii) Cl\(_{(g)}\) + e\(^{-}\) \(\to\) Cl\(^{-_(g)}\)

(f) State the effect of each of the following aqueous solutions on litmus paper: (i) Na\(_2\)SO\(_{4(aq)}\) (ii) AlCl\(_{3(aq)}\)

(g) Define the term efflorescence.

(h) Give two uses of activated charcoal.

(i) State one use of each of the following processes in the chemical industry: (i) hydrogenation of vegetable oil; (ii) cracking; (iii) esterification.

(j) Calculate the amount of silver deposited in moles when 10920 coulombs of electricity is passed through a solution of a silver salt. [ Faraday constant-- 96500 C mol\(^{-1}\)]

Question 48:

• WAEC 2014

(a) Define each of the following terms:
(i) ion; (ii) isotopes.

(b)(i) Consider the:element \(_{12}\)Mg and \(_{3}\)Al
I. Write the electron configuration of each element. II. Explain briefly why the first ionization energy of \(_{12}\)Mg is greater than that of \(_{13}\)Al.
(ii) Write the formulae of three different oxides of period 3 elements that react with water.

(c)(i) What are allotropes?
(ii) Name the two crystalline allotropes of carbon.
(iii) Give one industrial use of each allotrope named in (c)(ii).

(d) On warming crystals of sodium chloride with concentrated tetraoxosulphate (VI) acid, a gas was evolved.
(i) List two physical properties of the gas produced.
(ii) Write a balanced equation for the reaction.

(e) A certain chip W used in a circuit of a microcomputer has a mass of 5.68mg. Calculate the amount of W in the microcomputer. [ W = 28 gmol\(^{-1}\) ].

Question 49:

• WAEC 2014

(a)(i) Outline the steps involved in the purification of water for town supply.
(ii) Give two cations that can cause hardness in water.
(iii) State two disadvantages of hardness of water.
(iv) List two sources of water pollution.

(b)(i) Explain briefly why water is a good solvent for sodium chloride but not for oil.
(ii) State the function of H\(_2\)SO\(_4\) in each of the following reaction equations:
(i) C\(_2\)H\(_5\)OH\(_{(l)}\) \(\to\) C\(_2\)H\(_{4(g)}\)
(ii) MgO\(_{(s)}\) + H\(_2\)SO\(_4\)\(_{(aq)}\) —> MgSO\(_{4(aq)}\) + H\(_2\)O\(_{(l)}\)
(iii) C\(_{(s)}\) + conc. H\(_2\)SO\(_4\) --> CO\(_{(g)}\) + SO\(_{2(g)}\) + H\(_2\)O\(_{(l)}\)

(c) (i) Give the two products formed when chlorine water is exposed to sunlight.
(ii) I. Which of the compounds is suitable for the preparation of standard alkaline solution?
II. Give a reason for your answer in (c)(ii)I

Question 50:

• WAEC 2014

(a)(i) Explain briefly each of the following terms: I. anode; II. cathode.
(ii) Sodium and aluminium are extracted by the electrolysis of molten sodium chloride and alumina respectively. Write balanced equations for the reactions at the anode and cathode during the extraction of: I. sodium; II. aluminium.
(iii) Explain briefly why extraction of aluminium is considered environmentally friendly while that of sodium is not.

(b) Consider the reaction represented by the following equation:
K\(_2\)Cr\(_2\)O\(_7\) + HC1--> KCI + CrCl\(_3\) + H\(_2\)O + Cl\(_2\)
(i) Explain briefly why this reaction is redox.
(ii) Write balanced half equations for the reaction.
(iii) Write the over-all balanced reaction equation.

(c) During the electrolysis of molten Al\(_2\)O\(_3\), a current of 6A was passed through the electrolyte for 1 hr. 30 mins. Calculate the mass of aluminium deposited at the cathode.