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CHEMISTRY (Objective Questions And Answers)


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THEORY QUESTIONS
WAEC SYLLABUS

WASSCE 2018

Objectives



1. Which of the following raw materials is used in the plastic industry?

(a) Ethene

(b) Methane

(c) Sulphur

(d) Hydrogen.


2. Which of the following organic compounds can undergo both addition and substitution reactions?

(a) Petane

(b) Benzene

(c) Propane

(d) Hexane.


3. Which of the following equations represents a redox reaction?

(a) AgNO3(aq) + KCI(aq) AgCI(s) + KNO3(aq)

(b) HNO3(aq) + NaCH(aq) + NaNO3(aq) + H20(1)

(c) CaC03(s) CaO(s) + C02(g)

(d) 2H2S(g) + S02(g) 2H2O(I) + 3S(p)


4. The process of extraction of iron from its ore is

(a) Decomposition

(b) Oxidation

(c) Reduction

(d) Sublimation.


5. What is the solubility of a salt if 0.45 of it is obtained on evaporating 200cm3 of its saturated solution to dryness?

(a) 0.085dm-3

(b) 2.005dm-3

(c) 8.005dm-3

(d) 80.005dm-3.


ANSWERS

6. An acidic salt has

(a) double anions in its aqueous solution

(b) a single cation in its aqueous solution

(c) hydrogen ions in its aqueous solution

(d) hydrogen atoms in its aqueous solution.


7. A reaction is endothermic if the

(a) reaction vessel feels cool during the reaction

(b) enthalpy change is negative

(c) bond forming energy exceeds bond breaking energy

(d) heat off formation of reactants exceeds heat of formation of ` products.


8. In which of the following compounds does hydrogen form ionic compound?

(a) GH4

(b) HCI

(c) NH3

(d) NaH.


9. Consider the following reaction equation: Br2 + 2KI ---> 2KBr + 12, Bromine is reacting as

(a) an oxidizing agent

(b) a reducing agent

(c) an acid

(d) a base.


10. An organic compound has the empirical formula CH2. If its molar mass is Algmof1-, what is its molecular formula? [H = 1.0, C = 12.0]

(a) C2 H4

(b) C3 H4

(c) C3 H6

(d) C4 H8


ANSWERS

11. Ethene is produced from ethanol by

(a) decomposition

(b) hydrolysis

(c) ozonolysis

(d) dehydration.


12. Consider the following equilibrium reaction. 2AB(g) + B2(g) <===> 2 AB3(g, AH = - Xkjmol-1 the backward reaction will be favored by

(a) a decrease in pressure

(b) an increase in pressure

(c) a decrease in temperature

(d) an introduction of a positive catalyst.


13. What is the mass of solute in 500cm3 of 0.005mofdm-3 H2SO4? [H = 1.0, O = 16.0 S = 32.0]

(a) 0.490g

(b) 0.049g

(c)0.245g

(d) 0.0245g


14. Pure water can be made to boil at a temperature lower than 0 by

(a) reducing its quantity

(b) decreasing the external pressure

(c) distilling it

(d) increasing the external pressure.


15. Consider the following sketch of the solubility curve of some substances.





At what temperature does the solubility of KNO3 equal that of -NaNOv?

(a) 0°C

(b) 20°C

(c) 30°C

(d) 40°C


ANSWERS

16. When a salt added to its saturated solution, the salt

(a) dissolves and the solution becomes super saturated

(b) dissolves and the solution becomes unsaturated

(c) precipitates and the solution remains unchanged

(d) dissolves and crystals are formed.


17. When substance X was added to a solution of bromine water, the solution become colourless. X is likely to be

(a) propane

(b) propanoic acid

(c) propyne

(d) propanol.


18. The preferential discharge of ions during electrolysis is influenced by the

(a) mechanism of electrolysis

(b) electrolytic reactions

(c) nature of the electrode

(d) type of electrolytic cell.


19. The valence electrons of 12Mg are in the

(a) 3s orbital

(b) 2px orbital

(c) 2s orbital

(d) 1s orbital.


20 Stainless steel is an alloy comprising of

(a) Fe and C

(b) Fe and Ni

(c) Fe, C and Ni

(d) Fe, C and Al


ANSWERS

21. The number of hydrogen ions in 1.0dm3 of 0.02mofdm-3 tetraoxosulphate (VI) acid is [A + = 6.02 x l023]

(a) 12 x l022

(b) 1.2 x 1023

(c) 2.4 x 1022

(d) 2.4 x 1023


22. The most suitable substance for putting out petrol fire is

(a) water

(b) carbon(lV)oxide

(c) fire blanket

(d) sand.


23. The following factors would contribute to environmental pollution except

(a) production of ammonia

(b) manufacture of cement

(c) photosynthesis

(d) combustion.


24. The position of equilibrium in a reversible reaction is affected by

(a) particle size of the reactants

(b) vigorous stirring of the reaction mixture

(c) presence of a catalyst

(d) change in concentration of reactants.


25. The diagram below illustrates conical flask containing water and ice. Which of the following statements about the diagram is correct?





(a) the water is at a lower temperature than the ice

(b) energy is absorbed when the ice changes to water

(c) energy is released when the ice changes to water

(d) the water molecules vibrate about a fixed point.


ANSWERS

26. Which of the following statements best explains the differences between a gas and a vapour?

(a) unlike gases, vapours are liquids at room temperature

(b) unlike gases, vapour can easily be condensed into liquids

(c) unlike gases, vapor is readily converted into solids

(d) vapours are generally denser than gases.


27. Consider the following reaction equations: 2HCI + Ca(OH)2 CaCI2 + H2O. What is the volume of 0.1 moldm-3 HCI that would completely neutralize 25 cm3 of 0.3 MOLDM-3 Ca(OH)2?

(a) 150cm3

(b) 75cm3

(c) 30cm3

(d) 25cm3


28. Cu and HN03 are not suitable for preparing hydrogen gas because of their

(a) reactivity and oxidation respectively

(b) conductivity and corrosiveness respectively

(c) melting point and reduction respectively

(d) electronegativity and solubility respectively.


29. Which of the following formula cannot be empirical formula?

(a) CH

(b)2

(c)26

(d)24


30. One of the criteria for confirming the purity of benzene is to determine its

(a) heat capacity

(b) boiling point

(c) mass

(d) colour.


ANSWERS

31. When chlorine is passed through a sample of water, the pH of the water sample would be

(a) < 7

(b) > 7

(c) = 7

(d) 0.


32. How many atoms are contained in 0.2 MOLES of nitrogen? [NA = 6 02 x 1023 ]

(a)1.20 x 1023

(b) 2.41 x 1023

(c) 3.62 x 1023

(d) 4.82 X 1023


33. The strength of metallic bonds depends on the

(a) charge density of the atoms

(b) ductility of the metal

(c) number of valence electrons

(d) total number of electrons in the atom.


34. When is added to 3 solution, crystals of silver forms on surface. This indicates that is

(a) oxidized

(b) reduced

(c) decomposed

(d) dissociated.


35. The empirical formula of a compound containing 0.067 MOL Cu and 0.066 MOL O is [Cu = 63.5,0 = 16.01]

(a) Cu20

(b) CuO

(c) CuO2

(d) Cu2O2


ANSWERS

36. The change in the oxidation state of iron in the reaction represented by the equation below is 2FeCI2 + H2S 2

(a) +2 to + 3

(b) + 3 to + 2

(c) 0 to + 2

(d) +3 to 0.


37. Which of the following methods can be used to separate blood cells from plasma?

(a) centrifugation

(b) filtration

(c) chromatography

(d) distillation.


38. Which of the following statements about ionic radius is correct? Ionic radius

(a) increase as nuclear charge increases

(b) decreases as nuclear charge increases

(c) decreases as nuclear charge decreases

(d) remains constant as nuclear charge increases.


39. Analysis of a hydrocarbon shows that it contains 0.935 of carbon per gram of the compound. The mole ratio of carbon to hydrogen in the compound is [H = 1.0 C = l2.0]

(a) 1:1

(b) 1:2

(c) 2:1

(d) 2:3.


40. The law of definite proportions states that

(a) pure samples of the same compound contains the same elements combined in the same proportion by mass

(b) pure samples of substances are in the same proportion by mass

(c) chemical compounds are pure because they contain the same elements

(d) matter can neither be created or destroyed.


ANSWERS

41. What is the relative molecular mass of a compound which has empirical formula CH2O? [H = 1.0, C = 12.0,0 = 16.0]

(a) 42

(b )45

(c) 126

(d) 180.


42. Atoms are electrically neutral because they

(a) do not conduct electricity

(b) contain equal number of protons and electrons

(c) are composed of neutrons and electrons

(d) cannot be attracted by electromagnetic field.


43. Common salt (NaCl) is used for preserving foods. Which of the following properties could be used to determine its purity before use?

(a) solubility in water

(b) melting point

(c) relative density

(d) crystalline nature.


44. Which of the following electron configurations represents the transition element chromium (24Cr)?

(a) 1s22s2 2p6 3s2 3p6 4s2 3d4

(b) 1s2 2s2 2p6 3s2 3p63d6

(c) 1s22s22p63s23p44s'

(d)1s22s22p6 3s23p64s13d5


45. The atomic number of an isotope of hydrogen is equal to its mass number because it

(a) has a totally filled valence shell

(b) has a high charge to mass ratio

(c) does not contain neutrons

(d) exhibits isotopy.


ANSWERS

46. The total number of shared pair of electrons in the compounds below is.





(a) 5

(b) 6

(c)10

(d) 12.


47. The bonding pair of electrons in a hydrogen chloride molecule is pulled towards the chlorine atom because

(a) chlorine has a larger atomic size

(b) chlorine has a larger atomic mass

(c) chlorine is more electronegative

(d) there is no bonding orbitals within the hydrogen atom


48. The solubility of C02in water can be accounted for by

(a) van der Waal's forces

(b) ionic attraction

(c) dipole attraction

(d) covalent bonding.


49. Which of the following properties would not influence electrovalent bond formation?

(a) electronegativity

(b) electron affinity

(c) ionization potential

(d) catalytic ability.


50. Particles in a solid exhibit

(a) vibrational motion only

(b) vibrational and translational motion

(c) vibrational and random motion

(d) random and translational motion.



WASSCE JUNE 2018 CHEMISTRY OBJECTIVE TEST

ANSWERS

​1. A 2. B 3. D 4. C 5. B 6. C 7. A 8. B 9. A 10. C

11. D 12.A 13. C 14. B 15. B 16. A 17. C 18. C 19. A 20. C

21. A 22. A 23. C 24. D 25. B 26. B 27. A 28. A 29. D 30. B

31. A 32. A 33. B 34. A 35. B 36. B 37. A 38. B 39. A 40. A

41. B 42. A 43. A 44. A 45. D 46. B 47. C 48. C 49. D 50. B


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