Chemistry 2020 Past Questions | WAEC
31. What is the solubility of the salt at 30°C? [CuSO4= 160]
- A. 0.031
- B. 0.125
- C. 0.640
- D. 1.560
32. The bond between NH3and H+in NH4+ is?
- A. dative
- B. covalent
- C. hydrogen
- D. electrovalent
33. Which of the following oxides has a giant covalent structure?
- A. Al2O3
- B. Na2O
- C. P4O10
- D. SiO2
34. Which of the following hydroxides is not readily soluble in water?
- A. NH4OH
- B. Ca(OH)2
- C. NaOH
- D. KOH
35. Which of the following statements about the solubility of a salt is correct?
- A. A salt whose solubility increases with temperature would not crystallize easily on cooling
- B. A salt whose solubility is independent of temperature would normally crystallize out on cooling
- C. Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature
- D. Solubility of a solid does not affect its crystallization
36. How many moles of H2SO4 are there in 50 cm3of 0.108 mol dm33solution of the acid?
- A. 5.4x 10
- B. 5.4 x 10−3
- C. 5.4x 10−1
- D. 5.4 x 10−2
37. If 20 cm3of sodium hydroxide was neutralized by 20 cm3 of 0.01 mol dm3 tetraoxosulphate(VI) acid, what is the concentration of the solution?
- A. 0.010
- B. 0.020
- C. 0.100
- D. 0.150
38. “Electrons always occupy the lowest empty energy level” is a statement of
- A. Aufbau Principle
- B. Hund’s rule
- C. Pauli Exclusion Principle
- D. Periodic law
39. Which of the following metals does not react with water to produce hydrogen?
- A. Copper
- B. Potassium
- C. Sodium
D. Zinc
40. Which of the following arrangement of elements is in decreasing order of electronegativity?
- A. Na, Mg, Al, Si, P
- B. Na, A1, Mg, P, Si
- C. P, Mg, Na, Si, Al
- D. P, Si, Al, Mg, Na
41. The metallic bond in magnesium is stronger than that in calcium because magnesium has a
- A. larger atomic size.
- B. smaller atomic size
- C. greater number of valence electrons
- D. lower melting point
42. Consider the reaction represented by the following equation:
AgNO3 + NaCl → AgCl + NaNO3.
The steps that could be taken to obtain pure dry sample of AgCI (s) from the mixture includes
- A. heating to saturation and drying
- B. filtering and evaporation to dryness
- C. filtering, washing and drying
- D. crystallizing and allowing to cool
43. How many electrons does 3115P3contain?
- A. 12
- B. 15
- C. 16
- D. 18
44. The atomic number of an atom would be equal to its mass number if it
- A. has a totally filled valence shell
- B. has a high charge to mass ratio
- C. does not contain neutrons
- D. exhibits isotopy
45. Which of the following processes is not exhibited by atoms in order to attain more stable electron configuration?
- A. Gaining of electrons
- B. Hybridization of orbitals
- C. Losing electrons
- D. Sharing electron
