Waec Chemistry 2015 Past Questions and Answers

Question 51:

• WAEC 2015

Consider the following equilibrium system:
2SO_2(g) + O_2(g) \(\rightleftharpoons\) 2SO_3(g)
The addition of more O_2(g) to the system will shift the equilibrium position to the

A. Right leading to the production of more SO_3(g)
B. Right leading to the production of more SO_2(g)
C. Left leading to the production of more SO_2(g)
D. Left leading to the production of more SO_3(g)

Question 52:

• WAEC 2015

(a) Define esterification.
(b) State two properties of plastic.
(c) Name the components of duralumin.
(d) What is meant by each of the following terms?
(i) Raw material.
(ii) Primary product.
(e) State Charles' law.
(f) List four pieces of protective equipment in the laboratory.
(g) Give two uses of ammonia.
(h) Name the:
(i) process by which lighter hydrocarbons are obtained from heavier ones;
(ii) products formed from the reaction between ethanol and sodium metal.
(i) Determine the oxidation number of sulphur in H\(_2\)SO\(_4\).
(j) Write the IUPAC name for each of the following compounds: (i) NaClO\(_3\); (ii) CuSO\(_4\)5H\(_2\)O.

Question 53:

• WAEC 2015

(a) Consider the following table; (i) Which of the elements:

Element	Atomic Number	Mass Number
J	9	19
Q	13	27
R	16	32
X	19	39
Y	24	52

I. is a halogen?
II. is most likely to be attracted by a magnet?
III. belongs to group I?
IV. would readily form an ion with a double negative charge?

(ii) What type of bond would exist between J and X when they combine?
(iii) How many neutrons are there in Q?
(iv) Write the formula of the compound formed when R combines with X.
(v) State the element which exists as diatomic molecule..
(vi) Select the element which belong to the d-block of the periodic table.

(b)(i) Explain briefly the term atomic orbital
(ii) I. State three prostulates of Dalton's atomic theory.
II. List two limitations of this theory in the study of the atom
(iii) Describe briefly the structure of sodium chloride in its solid state.

(c) A sample of carbon is burnt at a rate of 0.50g per second for 30 minutes to generate heat.
(i) Write a balanced equation for the reaction
(ii) Determine the:
I. volume of carbon (IV) oxide produced at s.t.p.
II. moles of oxygen used up in the process at s.t.p. [C = 12.0, O = 16.0, Molar volume V\(_m\) = 22.4 dm\(^3\)].

Question 54:

• WAEC 2015

(a)(i) Give three characteristics of homologous series.
(ii) Name two groups of compounds which form such a series.

(b) A saturated organic compound A containing two carbon atoms reacted with ethanoic acid in the presence of a mineral acid to form a compound B with a sweet smell. (i) Name the functional group present in A.
(ii) Draw the structure of A.
(iii) Write a chemical equation to show the formation of B.
(iv) Name the compound B.

(c)(i) Write a balanced equation for the reaction between ethyne and excess bromine.
(ii) Give IUPAC name of the product of the reaction in (c)(i)
(iii) State two conditions under which cracking takes place

(d)(i) Outline the preparation of ethanol from starch.
(ii) Give two properties of starch.
(iii) Give a reason why starch does not reduce Fehlings solution
(iv) Describe briefly a chemical test to confirm the presence of starch.

Question 55:

• WAEC 2015

(a)(i) Name two gases that could be used to perform the fountain experiment.
(ii) State the physical property which makes the gases suitable for the experiment in (a)(i)
(b)(i) Define each of the following terms: I. solubility; II. saturated solution.
(ii) State two factors that affect the solubility of a solid in a liquid.
(iii) A salt Z of mass 10.2 g was dissolved in 15.4 cm\(^3\) of distilled water at 40°C. Calculate the solubility of Z in moldm\(^3\) at 40°C. [Mr (Z) = 331].
(c)(i) Town water supplies that have passed through iron pipes contain P and Q ions. In the presence of air, P ions are slowly converted to Q ions.
I. Identify P and Q ions. II. Write a balanced equation for the reaction between P ions, hydrogen ions and oxygen to give Q ions and water.
(ii) Explain briefly a test to confirm the purity of water.
(iii) State the effect of:
I. boiling a temporally hard water. II. adding sodium trioxocarbonate (IV) crystals to permanent hard water;
(iv) Write a balanced equation for the process in (c)(iii)I.