Chemistry 2020 Past Questions | WAEC

Study the following Chemistry past questions and answers for JAMBWAEC  NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

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

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