Chemistry 1999 Waec Past Questions and Answers

Question 41 :

• WAEC 1999

Which of the following is needed to produce slag during the extraction of iron in the blast furnace?

A. Cryolite
B. Limestone
C. Carbon
D. Sulphur

Question 42 :

• WAEC 1999

Environmental pollution problems are generally more severe in countries which have

A. Dense population
B. Low birth rate
C. Great land mass
D. Limited industries

Question 43 :

• WAEC 1999

The greenhouse effect is a climatic condition associated with the presence of excess

A. Carbon (IV) oxide
B. Hydrogen sulphide
C. Nitrogen (ll) oxide
D. Ammonia gas

Question 44 :

• WAEC 1999

(a)(i) State three postulates of the kinetic theory of gases.
(ii) Draw a sketch to illustrate Boyle's law.
(iii) Explain what is meant by "absolute zero of temperature".
(b) Equal volumes of a gas X and oxygen are at the same pressure but temperature of 200 K and 800K respectively.
(i) Giving reason for your answer, state which of the gas samples contains the greater number of molecules.
(ii) If the mass of one molecule of the gas X is 2.19 x 10\(^{-22}\) g, determine the molar mass of X. [Avogadro constant = 6.02 x 10\(^{-23}\)]
(iii) Hence, state with reason which of X and oxygen will diffuse faster under the same conditions. [O= 16].
(c)(i) Mention two reaction conditions that can increase the yield of ammonia in the reaction represented by the following equation: N\(_{2(g)}\) + 3H\(_{2(9)}\) \(\rightleftharpoons\) 2NH\(_{3(g)}\) \(\Dellta\)H = -46kJmol\(^{-1}\). Draw a labelled energy profile diagram for an endothermic reaction.
(iii) A solid W decomposes on heating according to the following equation: W\(_{(s)} \to Y_{(s}) + Z_{(g)}\) List two factors apart from temperature, which can affect the rate of the reaction.

Question 45 :

• WAEC 1999

a)(i) State three differences between covalent compounds and electrovalent compounds.
(ii) Two elements represented as K and L have atomic numbers of 12 and 8 respectively. Write their electronic structures and state the group to which each belongs in the Periodic Table.
(iii) If an alkali metal M exists naturally as the oxide, state with reason whether or not M can be extracted by reduction of the oxide with coke.

(b)(i) What is meant by the half-life of a radioactive element?
(ii) Mention the radioactive isotope used in dating archaeological specimens.
(iii) Balance the following equation and identify Q,
\(^{28}_{13}Al\) —> \(^{24}_{13}Si + \(^{0_1Q\)

(c)(i). Give three chemical properties of metals.
(ii) State two reasons why duralumin preferred to steel in aircraft manufacture.
(iii) What term is used to describe the ability of metals to be hammered into thin sheets?
(iv) Calculate the number of mole of electrons involved in the oxidation of 2.8g of iron filings to iron (II) ions. [Fe = 56].