Chemistry 2005 Waec Past Questions and Answers

Question 36 :

• WAEC 2005

Which of the following pairs of solutions will produce a precipitate when mixed?

A. Pb(NO₃)_2(aq) and NaCI_(aq)
B. MgSO_4(aq) and HCI_(aq)
C. ZnCI_2(aq) and NaSO_4(aq)
D. NaOH_(aq) and HNO_3(aq)

Question 37 :

• WAEC 2005

Which of the following substance is an alloy of lead?

A. Brass
B. Duralumin
C. Stainless steel
D. Soft solder

Question 38 :

• WAEC 2005

In which of the following processes is biotechnology not applied?

A. Manufacture of drugs
B. Treatment of domestic sewage
C. Production of alcoholic beverages
D. Electroplating of metals

Question 39 :

• WAEC 2005

(a) The electronic configurations of atoms of elements A, B, C and D are given as follows: A. Is\(^2\)2s\(^2\)2p\(^2\); B. 1s\(^2\)2s\(^2\)2sp\(^1\) ; C. 1s\(^2\)2s\(^2\) 2p\(^1\) ; D. 1s\(^2\) 2s\(^2\)
(I) Arrange the elements in order of increasing atomic size, giving reasons
(ii) State which of the elements I. is divalent II. contains atoms with two unpaired electrons in the grouped state. Ill, readily loses one electron from its atom during chemical bonding IV. belongs to group Ill in the Periodic Table.

(b)(i) State one difference between electrovalent and covalent bonds.
(ii) Name two other bonds apart from the ones in (b)(i) above which bind atoms and molecules together.
(iii) State two characteristics of a covalent compound.

(c)(i) What is isotopy?
(ii) Illustrate with suitable example
(iii) Two isotopes of Z with mass numbers 18 and 20 are in the ratio 1:2 Determine the relative atomic mass of Z.

(d)(i) Which of the following elements: calcium, fluorine, iodine neon, magnesium and helium are I. halogens II. noble gases Ill. alkaline earth metals.
(ii) Write a balanced equation for the bombardment of \(^7_3Li\) with protons to produce \(^8_4\beta\) and \(\gamma\)-rays
(iii) State one use of radioactive isotopes.

Question 40 :

• WAEC 2005

(a)(i) State Graham's law of diffusion
(ii) If 100 cm\(^3\) of oxygen diffused in 4 seconds and 50cm\(^3\) of gas Y diffused in 3 seconds, calculate the relative molecular mass of gas Y. (0 = 16)

(b) Consider the following equilibrium reaction: X + 2Y\(_{(g)}\) \(\rightleftharpoons\) XY\(_{2(9)}\) \(\Delta\)H = -52KJ mol\(^{-1}\)
(i) State what happens to the yield of XY\(_2\) when the temperature is increased
(ii) Explain the effect of decrease in pressure on the equilibrium position.
(iii) State the effect of a catalyst on the I. position of equilibrium II. activation energy

(c)(i) State the differences between the solubilities of solids and gases in liquids.
(ii) Name the physical-properties used it choosing separation techniques for the following mixtures:
I. kerosene and petrol II. calcium trioxocarbonate (IV) and potassium chloride. III. ammonium chloride and sodium chloride.

(d)(i) State a method of preparing each of the following salts:

Acid	Basicity
H\(_3\)PO\(_4\)
CH\(_3\)COOH
HNO\(_2\)

(iii) State the difference between anhydrous and hydrated salts.