Chemistry Exam Past Questions and Answers | JAMB, WAEC and NECO

Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.

• Question 121: MnO_4(aq) + 8H + _(aq) + 5Fe²⁺ → Mn^2+(aq) + 4H₂O_(I). The oxidation number of manganese in the above reaction changed from? Options:
  A) +7 to +2
  B) +6 to +2
  C) +5 to +2
  D) +4 to +2
  Show Answer
  The correct answer is A .
• Question 122:

  

  What is the IUPAC name for the hydrocarbon?

  Options:
  A) 2-ethyl-4-methylpent-2-ene
  B) 3,5-dimethylhex-3-ene
  C) 2,4-dimethylhex 3-ene
  D) 2-methyl-4-ethylpent-3-ene
  Show Answer
  The correct answer is A .
• Question 123:

  200cm³ each of 0.1M solutions of lead (II) trioxonitrate (V) and hydrochloric acid were mixed. Assuming that lead (II) chloride is completely insoluble, calculate the mass of lead (II) chloride that will be precipitated.

  [Pb = 207, Cl= 35.5, N = 14, O = 16]

  Options:
  A) 2.78g
  B) 5.56g
  C) 8.34g
  D) 11.12g
  Show Answer
  The correct answer is B .
• Question 124:

  In the laboratory preparation of oxygen, the gas cannot be collected by displacement of air because

  Options:
  A) the density of oxygen is greater than that of air
  B) the density of air is nearly the same as that of oxygen
  C) oxygen is a component of air
  D) air is an impure substance
  Show Answer
  The correct answer is A .
• Question 125:

  An organic compound which liberate carbon(iv)oxide from trioxocarbonate(iv) solution is likely to be?

  Options:
  A) C${}_2$H${}_5$OH
  B) C${}_3$H${}_4$
  C) C${}_6$H${}_6$
  D) CH${}_3$COOH
  Show Answer
  The correct answer is D .
• Question 126: Which of the following will produce a solution with pH less than 7 at equivalent point? Options:
  A) HNO ₃ +NaOH
  B) H ₂SO ₄ + KOH
  C) HC +Mg (OH) ₂
  D) HNO ₃ + KOH
  Show Answer
  The correct answer is C .
• Question 127:

  The percentage of water of crystallization in ZnSO₄.7H₂O is

  [Zn = 65, S = 32, O = 1, H = 1]

  Options:
  A) 33%
  B) 44%
  C) 55%
  D) 87%
  Show Answer
  The correct answer is B .
• Question 128: The solution of a sample in a tube will be identified as a chloride if it gives Options:
  A) a white precipitate on addition of AgNO₃ and barium chloride solutions
  B) a white precipiate when acidified with HCI, and then AgNO₃ solution added
  C) a white precipitate when acidified with dilute HNO₃ and then AgNO₃ solution added
  D) a white precipitate when acidified with dilute H₂SO₄ and then barium nitrate solution added
  E) a pungent smell of chlorine gas when dilute HCI and MnO₂ are added
  Show Answer
  The correct answer is C .
• Question 129: The energy change (ΔH) for the reaction CO(g) + (1)/(2)O_2(g) → is?(ΔHi(CO) = -110.4 kJ mol^-) (ΔHi(CO₂) = -393 kJ mol^-) Options:
  A) -503.7 kJ
  B) +503.7kJ
  C) -282.9 kJ
  D) +282.9 kJ
  E) +393.3 kJ
  Show Answer
  The correct answer is C .
• Question 130: When at equilibrium, which of the reactions below will shift to the right if the pressure is increased and the temperature is kept constant? Options:
  A) 2SO_3(g) ↔ 2SO_2(g) + O_2(g)
  B) 2CO_2(g) ↔ 2CO_(g) + O_2(g)
  C) 2H_2(g) + O_2(g) ↔ 2H₂O_(g)
  D) 2NO_(g) ↔ N_2(g) + O_2(g)
  Show Answer
  The correct answer is C .