enwaecchemistry2007

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THEORY QUESTIONS

WAEC SYLLABUS

1. When sodium atom forms the ion Na+,

A. it gains one electron

B. it gains one proton

B. it achieves a noble gas configuration

C. its atomic number increases.

2. Which of the following statements about rare gasses are correct? I. Their outermost shells are fully filled. II. They are generally unreactive. III. Their outermost shells are partially filled. IV. They have lone pair of electrons in their outermost shell.

A. I and II only

B. II and III only

C. l, II and III only

D. I.II,III and IV

3. How many electrons are in the ion F" ? [¹⁹F ]

A. 8

B.9 ⁹

C.10

D.19

4. What is the value of x in the following nuclear reaction equation? ¹¹B + ²⁵¹₉₈Cf x Lr + 3¹₀n

A. 241

B. 259

C. 261

D. 265

5. Which of the following properties is characteristic of the halogens?

A. Ability to accept electrons readily

B. Ability to donate electrons readily

C. Ability of form basic oxides

D. Formation of coloured compounds

ANSWERS

6. In which of the following atoms is the ionic radius larger than the atomic radius? [₁₁Na, ,₁₂Mg, ₁₃AI, ₁₇CI]

A. Aluminum

B. Chlorine

C. Magnesium

D. Sodium

7. A transition metal would be expended to

A. form oxides with different formulae

B. have strong oxidizing ability

C. have low density

D. have an atomic structure with an incomplete outermost shell.

8. Which of the following properties of atoms generally increases down a group in the periodic table?

A. Electron affinity

B. Electronegativity

C. Ionic radius

D. Ionization energy

9. Which of the following statements about sodium is not true?

A. Na+ is smaller in size than Na

B. Na is smaller in size than Na+

C. Na+ has fewer electrons than Na

D. The effective nuclear charge in Na+ is greater than in Na

10. If the difference between the electronegativities of two elements is large, the type of bond that can be formed between them is

A. covalent

B. dative

C. ionic

D. metallic

ANSWERS

11. Which of the following species does not contain a co-ordinate bond?

A. AI₂CI₆

B. CCL₄

C. H₃0⁺

D. NH⁺₄

12. Which of the following compounds has hydrogen bonds between its molecules?

A HF

B. HBr

C. HCI

D.HI

13. 14.8g of a salt (z) dissolved in 250 cm³ of distilled water gives a concentration of 0.80 mole dm ³. Calculate the molar mass of the salt (z).

A. 13.5 g mol¹

B. 18.5 g mol¹

C.47.4 g mol^-1

D. 74.0 g mol¹

14. How many atoms are there in one mole of hydrogen gas? [Avogadro's c 6.02 x 10²³ mol¹]

A. 1.2 X10²³

B.6.0 x 10²³

C. 1.2 x 10²⁴

D.6.0 x 10²⁴

15. What is the percentage composition of oxygen in K₂Cr₂O₇? [K₂Cr₂0₇ = 294 O = 16 K = 39 Cr = 52]

A. 14.20%

B. 26.53%

C. 35.37%

D. 38.09%

ANSWERS

16. What is the IUPAC name of the compound represented by the molecular formular NaCI0₄?

A. Sodium tetraoxochlorate (I)

B. Sodium tetraoxochlorate (IV)

C. Sodium tetraoxochlorate (VI)

D. Sodium tetraoxochlorate (VII)

17. When air is successively passed through sodium hydroxide solution, alkaline pyrogallol and then concentrated tetraoxosulphate (VI) acid, its remaining components are

A. oxygen and water vapour

B. oxygen and nitrogen

C. carbon (IV) oxide and noble gases

D. nitrogen and noble gases

18. Which of the following gases is lighter than air?

A.CO₂

B.S0₂

C.HCI

D. NFI₁

19. Which of the following statements is true of the molecules of a gas under ideal conditions? The molecules

A. move at random

B. undergo inelastic collisions

C. attract each other

D. occupy a large volume.

20. In which of the following compound(s) will heat be absorbed on adding water?

I. KNO₃ II. Concentrated H₂S0₄ III. NHAI

A. I only

B. Ill only

C. I and III only

D. II and III only

ANSWERS

21. 25 cm³ of 0.80 mol dm ³ hydrochloric acid neutralized 20 cm³ of sodium hydroxide solution. What Is the concentration of sodium hydroxide in mol dm^-3?

NaOH_(aq) + HCI_(aq)-------> NaCI_(aq) + H₂0_(L)

A. 0.08

B. 0.10

C. 0.80

D. 1.00

22. Consider the reaction represented by the equation:

Ca(OH)_2(aq) + C0_2(g) > CaC0₃ + H₂0_(L) In the reaction above, C0₂act as

A. an acidic oxide

B. an oxidizing agent

C. a basic oxide

D. a dehydrating agent

23. Which of the following compounds is a basic salt?

A. Mg(N0₃)₂

B. (NH₄)₂S0₄

C. K₄Fe(CN)₆

D. Zn(OH)CI

24. What process is illustrated below? S_(s) <==H₂O==> S_(aq)

A. Decomposition of a solid

B. Melting of a solid

C. Formation of saturated solution of a solid

D. Sublimation of a solid.

25. A solution of a salt X reacts with AgN0₃ solution to give white precipitate which dissolves in excess aqueous ammonia. X contains

A. CI^-

B. Pb²⁺

C. SOI

D.Zn²⁺

ANSWERS

26. Consider the reaction represented by the following equation:

N_2(g)+ 3H_2(g) ------> 2NH_3(g) AH =-92kJmol^-1 Finely divided iron is used as catalyst in the reaction in order to

A. Lower the value of AH

B. Increase the time for attainment of equilibrium

C. Shorten the time for attainment of equilibrium

D. decrease the yield of ammonia

27. Which of the following factors will affect the rate of formation of S_(S) in the reaction represented by the equation below? S₂0²_3(aq) + 2H_(aq) S0_2(aq) + H₂0_(L) + S_(s)

A. Increase in temperature

B. Increase in pressure

C. Removal of H₂0_(L)

D. Use of a catalyst

28. In four separate experiments, the same quantity of magnesium ribbon was added to an excess of hydrochloric acid. In which of the experiments will hydrogen be given off most rapidly?