Welcome to our WAEC past question and answer series. In this post, we will be sharing Chemistry 2019 past questions and their answers for various subjects. Stay tuned enjoy while learning.
1. The periodic table is an arrangement of elements according to their?
A. Oxidation number
B. Atomic number
C. Mass number
D. Number of neutrons
2. A solid with higher melting and boiling points is likely to be?
A. Covalent compound
B. A Dative compound
C. An Electrovalent compound
D. A Non-metal
3. Which of the following metals reacts slowly with cold water?
A. Iron
B. Silver
C. Calcium
D. Potassium
4. Which of the following elements has the highest ionisation energy?
A. Calcium
B. Chlorine
C. Fluorine
D. Magnesium
5. The bleaching action of chlorine is through the process?
A. Hydration
B. Hydrolysis
C. Reduction
D. Oxidation
6. If 6.5g of magnesium ribbon reacts completely with Hydrochloric acid, how many grams of hydrogen gas would be liberated?
Mg(s) + 2 HCl(aq) –> MgCl 2(aq) + H 2(g)
[ H = 1.0, Mg = 24.0 ]
A. 0.54g
B. 0.70g
C. 1.08g
D. 1.40g
7. Calcium and magnesium belong to the group of the periodic table because both?
A. are metals
B. form cations
C. form colourless salts
D. have same number of valence electrons
8. Which of the substances is non-polar?
A. Bromine
B. Ammonia
C. Water
D. Hydrogen Bromide
9. Which of the following pairs of components have the same molecular mass?
[ H = 1.0, C = 12.0, O = 16.0 ]
A. Ethene and Ethyne
B. Ethane and Ethene
C. Carbon (ii) Oxide and Ethene
D. Carbon (iv) Oxide and Ethyne
10. When an equilibrium is established between dissolved and undissolved solutes, the solution is said to be?
A. Saturated
B. Unsaturated
C. Concentrated
D. Diluted
11. How many moles of carbon(iv)oxide contains 16.0g of oxygen?
[ C = 12.0, O = 16.0 ]
A. 0.20 mol
B. 0.25 mol
C. 0.40 mol
D. 0.50 mol
12. Stoichiometry is based on the law?
A. multiple proportion
B. constant composition
C. conservation of energy
D. conservation of mass
13. What is the percentage by mass of H in CH3COOH
A. 1.7%
B. 5.0%
C. 6.7%
D. 7.1%
14. Which of the following compounds has coordinate bonds in its structure?
A. Al2Cl6
B. MgCl2
C. AgCl
D. NaCl
15. The name of the compound CH3C(CH3)CH2CH2CH3
A. 2 – methyl butane
B. 2,2 – dimethyl butane
C. 2 – methyl pentane
D. 2,2 – dimethyl pentane
16. The properties of a good primary standard solution include the following except?
A. High molecular mass
B. low molecular mass
C. high degree of purity
D. readily available
17. What is the solubility of a salt X at 25ºC if the saturated solution of the salt contains 0.28g in 100cm3 of the solution in mol\dm3?
[ X = 56.0g ]
A. 0.05
B. 0.10
C. 2.60
D. 2.80
18. Vinegar is an aqueous solution of?
A. Hydrochloric acid
B. ethanedioc acid
C. ethanoic acid
D. hydrofluoric acid
19. Which of the following solutions containing one mole per dm3 of the compound would have the lowest PH?
A. ethanoic acid
B. hydrochloric acid
C. sodium chloride
D. sodium hydrogentrioxocarbonate(iv)
20. A sample of air was bubbled into water. The PH of the water slowly changed from 7 to 6. Which of the following gases in the samples caused the change?
A. carbon(iv)oxide
B. carbon(ii)oxide
C. nitrogen
D. oxygen
21. The most suitable indicator for the reaction between NaOH and HCOOH is?
A. bromocresol
B. methyl orange
C. methyl red
D. phenolphthalein
22. Consider the following reaction equation: 2Al(OH)3 + 3H2SO4 →Al2(SO4)3(aq)+6H2O. How many moles of tetraoxosulphate(vi)acid is needed to produce 0.5mol of aluminium tetraoxosulphate(vi)?
A. 0.5
B. 1.0
C. 1.5
D. 3.0
23. Which of the following pairs of substances has the highest heat of neutralisation?
A. strong acid and strong base
B. weak acid and weak base
C. strong acid and weak base
D. weak acid and strong base
24. When quicklime dissolves in water?
A. heat is absorbed
B. heat is evolved
C. oxygen is liberated
D. hydrogen is given off
25. If the value of ΔH is positive for a reaction, it means that the reaction is?
A. exothermic
B. endothermic
C. spontaneous
D. slow
26. Which of the following compounds is formed by the oxidation of ethanol?
A. C2H4CO2H
B. C2H5CO2H
C. CH3OH
D. CH3CO2H
27. What is the name of the gas liberated when diluted hydrochloric acid is added to iron(ii)sulphide?
A. turns lime water milky
B. decolorizes bromine water
C. gives a pop sound
D. turns lead(ii)ethanoate paper black
28. An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound?
[ H = 1.0. C = 12.0, O = 16.0 ]
A. C3H8O
B. C6H12O
C. C6H12O2
D. C12H12O11
29. When excess chlorine is mixed with ethane at room temperature, the product formed is?
A. 1,2-dichloroethane
B. 1,2-dichloroethene
C. 1,1-dichloroethane
D. 1,1-dichloroethene
30. Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol
A. H+ / K2Cr2O7
B. I2 / OH-
C. CH3COOH
D. NaCl
31. If a catalyst is added to a system, the temperature and the pressure remain constant, there would be no effect on the?
A. activation energy of the reaction
B. rate of the reaction
C. rate of the reverse reaction
D. heat of reaction
32. Consider the following reaction equation: 2NH3 .+ 3Cl2 → N2 + 6HCl.
NH3 is acting as?
A. a reducing agent
B. a dehydrating agent
C. a drying agent
D. an oxidising agent
33. The oxidation of chromium in Cr2O7)\(−2 )?
A. +4
B. +5
C. +6
D. +7
34. The process by which alkanoic acid reacts reversibly with alkanols is known as?
A. saponification
B. esterification
C. carboxylation
D. halogenation
35. If the oxidation potential of Mg and Al are +2.37 volts and + 1.66 volts respectively, then the Mg would?
A. not replace Al
B. be replaced by Al
C. remain in the solution
D. replace Al
36. Consider the reaction represented by the following equation: 2SO2 + O2 ⇌ 2SO3
A decrease in the pressure of the reaction would
A. decrease in the concentration of SO2
B. have no effect on the reaction
C. shift the equilibrium position to the left
D. shift the equilibrium position to the right
37. In a mixture of gases which do not react chemically together, the pressure of the individual gas is?
A. atmospheric pressure
B. vapor pressure
C. total pressure
D. partial pressure
38. Biotechnology is applied in the?
A. treatment of sewage
B. treatment of water
C. purification of chemicals
D. purification of metals
39. Which of the following organic compounds has the lowest boiling point?
A. C6H14
B. C5H12
C. C4H10
D. ( CH3 )3
40. Consider the following reaction represented by the following equation: C2H2 H\(2\)→ X H\(2\)→ Y. X and Y respectively are?
A. ethane and ethene
B. ethene and ethane
C. ethyne and ethene
D. ethane and ethyne
41. Which of the following substances can be classified as heavy chemicals?
A. CaOCl2
B. H2SO4
C. AgNO3
D. CaO
42. In Boyle’s law?
A. T is constant, P varies directly with V
B. P is constant, V varies inversely with T
C. V is constant, P varies directly with T
D. T is constant, V varies inversely with P
43. Which of the following apparatus is NOT used in volumetric analysis?
A. Pipette
B. Burette
C. Desiccator
D. conical flask
44. One of the deductions from Rutherford’s alpha particle scattering experiment is that?
A. electrons are negatively charged
B. electrons have a negligible mass
C. nuclei of atoms are positively charged
D. protons are positively charged
45. The atoms of 6429Cu and 6530Zn have the same number of?
A. nucleon
B. electrons
C. neutrons
D. protons
46. The number of electrons in the 3d orbital of 24Cr is
A. 2
B. 3
C. 4
D. 5
47. The method used to collect gas in the laboratory depends on its?
I. boiling point II. density III. smell IV. solubility in water
A. i and ii only
B. ii and iv only
C. iii and iv
D. i, ii, iii and iv
48. Which of the following methods is NOT used for the separation of mixtures?
A. Chromatography
B. Crystallisation
C. Distillation
D. Electrolysis
49. The group to which elements belong in the periodic table is determined by the number?
A. electrons
B. core electrons
C. valence shells
D. valence electrons
50. Kipps apparatus can be used to prepare?
A. H2
B. NH3
C. O2
D. H2S
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