enwaecchemistry2008

more

THEORY QUESTIONS

WAEC SYLLABUS

1. The mass spectrometer can be used to measure mass of

A. an atom

B. an electron

C a proton

D. a neutron

2. Find the number of neutrons in an atom represented by ⁴⁵₂₁X

A. 2I

B. 24

C. 45

D. 66

3. The valence electrons in a chloride ion are [₁₇ CI ]

A. 2p electrons only

B. 3s and 3p electrons only

C. 3p and 3d electrons only

D. 3p electrons only

4. What is the atomic number of an element whose cation Y⁺ has the electronic configuration Is₂2s₂ 2p₆

A. 9

B. 10

C. 11

D. 12

5. Atom ²³⁴₈₈Q decay by alpha emission to give an atom R. The atomic number and mass number of atom R are respectively.

A. 86 and 230

B. 87 and 234

C. 88 and 233

D. 90 and 238

ANSWERS

6. Which of the following statements is not true of halogens?

A. They exist in different physical states

B. They exist as diatomic molecules

C. Their ionic radii decrease down the group

D. Their melting and boiling points increase down the group

7. Elements in the same group of the periodic table have

A. The same number of valence electrons

B. The same number of electron shells

C. Different chemical behaviour

D. The same atomic size

8. Consider the following elements and their elect) configurations W: Is₂ 2s₂ X:ls₂2s₂2p₆ Y Is₂ 2s₂ 2p₆ 3s₂ Z: Is₂ 2s₂ 2p₆ 3s₂3p₂ Which of the elements belong to the same group in the periodic table?

A. Wand X only

B. Y and Z only

C. Wand Y only

D. W, Y and Z only

9. Arrange the following elements in order of increasing electron affinity: Br₂, CI₂, I₂ F₂^-

A. I₂, CI₂, Br₂, F₂.

B. I₂,Br₂,CI₂,F₂

C. CI₂, I₂, Br₂, F₂

D. Br₂, CI₂, I₂, F₂

10. Water molecules are held together by

A. covalent "bond

B. hydrogen bond

C. ionic forces

D. van der Waals forces

ANSWERS

11. The compound formed by two elements X and Y with the electronic configuration Is₂ 2s₂ 2p₄ and Is₂ 2s₂ 2p₆ 3s₂ respectively is

A. XY

B.YX

C.X₂Y₃ D. Y₂X₃

12. The force of attraction between covalent molecules is

A. dative bonding

B. hydrogen bonding

C. ionic force

D. van der Waals force

13. What is the mass of 6.02 x 10²⁴ atoms of magnesium? [ Mg = 24, Avogadro c 6.02 x 10²³ atoms mol^-1]

A. 240g

B. 24a

C. 2.4g

D. 0.24g

I4. Which of the following compounds with the corresponding masses contain the highest percentage of nitrogen? [N=14]

A NH, = 17

B. NH₄CI = 53.5

C. NH₄NO₃ = 80

D. (NH₃)₂ S0₄=132

15. If 5.00 cm³ of 0.20 mol dm^-3 Na,C0₃ was diluted with distilled water to obtain 250 cm³ solution, what is the concentration of the resulting solution?

A. 0.004-mol dm^-3

B. 0.02 mol dm^-1

C. 0.20 mol dm^-3

D. 0.40 mol dm^-3

ANSWERS

16. Which of the elements belong to the same group in the periodic table?

A. W and X only

B. Y and Z only

C. W and Y only

D. W, Y and Z only

17. Arrange the following elements in order of increasing electro affinity: Br₂, CI₂,I₂, F₂

A. I₂, CI₂. Br₂, F₂

B. I₂, Br₂, CI₂, F₂

C. CI₂, I₂, Br₂, F₂

D. Br₂, CI₂, I₂, F₂

18. Water molecules are held together by

A. covalent bond

B. hydrogen bond

C. ionic forces

D. van der Waals force

19. The compound formed by two elements X and Y with the electronic configuration

Is₂ 2s₂ 2p₄ and Is₂ 2s₂ 2p₆ 3s respectively is

A. XY

B.YX

C.X,Y,

D. Y,X₃

20. The force of attraction between covalent molecules is

A. dative bonding

B. hydrogen bonding

C. ionic force

D. van der Waals force

ANSWERS

21. What is the mass of 6.02 x 10²⁴ atoms of magnesium? [ Mg = 24, Avogadro c 6.02 x 10²³ atoms mol^-1]

A. 240g

B. 24g

C. 224g

D.0.24g

22. Which of the following compounds with the corresponding masses contain the highest percentage of nitrogen? [N=14]

A. NH₃ = 17

B. NH₄CI = 53.5

C. NH₄NO₃ = 80

D. (NH₃)₂ S0₄= 132

23. If 5.00 cm³ of 0.20 mol dm^-3 Na₂C0₃ was diluted with distilled water to obtain 250 cm³ solution, what is the concentration of the resulting solution?

A. 0.004 mol dm^-3

B. 0.02 mol dm^-3

C. 0.20 mol dm^-3

D. 0.40 mol dm^-3

24. Consider the reaction represented be the following equation:

Znl_(s)+ 2HCI_(aq)ZnCI_2(aq)+ H_2(g) What volume of hydrogen gas is produced at s.t.p. when 3.25 of zinc reacts with excess dilute HCI? [ Zn = 65, Molar gas volume at s.t.p. = 22.4 dm³ ]

A. 1.12dm³

B. 2. 24dm³

C. 4.48dm³

D. 8.96dm³

25. Which of the following gases has the lowest rate of diffusion under the same conditions of temperature and pressure? [H=l,O=16,Ne = 20, CI = 35.5]

A. Chlorine

B. Hydrogen

C. Neon

D. Oxygen

ANSWERS

26. In a fixed volume of a gas, an increase in temperature results in an increase in pressure due to an increase in the

A. number of collisions between the gas molecules

B. number of repulsion between the gas molecules

C. number of collision between the gas molecules and the walls of the container

D. kinetic energy of the gas

27. When concentrated HS0₄ is added to NaCI_(s), the gas evolved

A. bleaches damp blue litmus paper

B. forms a white precipitate with AgN0_3(aq)

C. forms a white precipitate with BaCI_(aq)

D. turns moist red litmus paper blue

28. The collision theory proposes that.

A. Reactants collide more frequently to bring about reduction in the reaction rate

B. all collisions of reactants are effective

C. Reactants must collide with a certain minimum amount of energy to form products

D. The fewer the collision the faster the reaction rate

29. Diamond does not conduct electricity because it

A. has no free valence electrons

B. is a giant molecule

C. contains no bonded electrons

D. is a solid at room temperature

Consider the energy profile diagram below and use it to answer question 30 to 32

ANSWERS

31. Enthalpy chance of the reaction is represented by

A. W

B. X

C. Z

D. Y

32. What type of reaction is represented by the energy diagram?

A. Endothermic

B. Exothermic

C. Redox

D. Neutralization

33. In dry Leelanche cell, manganese (IV) oxide acts as

A. a reducing agent

B. binding agent

C. catalyst

D. depolarizer

34. Oxidation takes place at the anode during electrolysis because the anode

A. is deficient in electron

B. is deficient in protons

C. has excess electrons

D. has attraction tor positive ions

35. Calculate the quantity of electricity passed when 0.4 A flow for 1 hour 20 minutes through an electrolytic cell

A. 4800C

B. 3840C

C. 1920C

D. 32C

ANSWERS

36. A mixture of kerosene and diesel oil can be separated by

A. crystallization

B. distillation %

C. precipitation

D. sublimation

37. Which of the following compounds would not give a precipitate with ammoniacal AgNO, solution?

A. CH₃C = CCH₃

B. HC = CH

C. CH₃C = CH

D. CH₃CH₂C = CH

38. When ethanol is heated with excess concentrated tetraoxosulphate (VI) acid, the organic product formed is

A. ethanal

B. ethanoic acid

C. ethane D. ethene

39. The hydrolysis of groundnut oil by potassium hydroxide is known as

A. hydrogenation

B. saponification

C. esterification

D. neutralization

40. What is the main type of reaction alkenes undergo?

A. Addition

B. Condensation

C. Elimination

D. Substitution

ANSWERS

46. A solution of a salt was acidified with HCI. When a few drops of BaCI₂solution were added, a white precipitate was formed. Which of the following anions is present in the salt?

A. CO₂^-3

B. NO₆³

C. SO₂^-4

D. SO₂^-3

47. Which of the following substances causes the depletion of the ozone layer in the atmosphere?

A. Carbon (IV)oxide

B. Chlorofluorocarbon

C. Sulphur (IV) oxide

D. Hydrocarbons

48. Chemicals that are produced in small quantities and very high degree of purity are

A. bulk chemicals

B. line chemicals