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 441:

  Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)

  From the equation above, the mass of magnesium required to react with 250cm³ of 0.5M HCl is

  [Mg = 24]

  Options:
  A) 0.3g
  B) 1.5g
  C) 2.4g
  D) 3.0g
  Show Answer
  The correct answer is B .
• Question 442:

  16.55g of lead (ll) trioxonitrate (V) was dissolved in 100g of distilled water at 20^oC, calculate the solubility of the solute in moldm-³

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

  Options:
  A) 0.05 g
  B) 2.00 g
  C) 1.00 g
  D) none of the above
  Show Answer
  The correct answer is D .
• Question 443: The reaction between hydrogen and iodine may be represented by the equation H₂(g)+ I₂(g) → 2HI(g), and is exothermic. Therefore Options:
  A) an increase in temperature favours the forword reaction
  B) an increase in pressure favours the backward reaction
  C) both pressure and temperature muct be increased to favour the forward reaction
  D) a decrease in temperature will favour the forward reaction
  E) a decrease in pressure and an increase in temperature will favour the forward reaction
  Show Answer
  The correct answer is D .
• Question 444: How many cations will be produced from a solution of potassium aluminium tetraoxosulphate (VI)? Options:
  A) 3
  B) 4
  C) 1
  D) 2
  Show Answer
  The correct answer is D .
• Question 445:

  L . Evaporation. ll. Sublimation. lll. Diffusion. IV. Brownian motion.

  Which of the above can correctly be listed as evidences for the particulate nature of matter?

  Options:
  A) I and lll only
  B) ll and lV only
  C) l, ll and lll only
  D) l, ll, lll and lV
  Show Answer
  The correct answer is D .
• Question 446: The process of converting linear alkanes to branched chain and cyclic hydrocarbons by heating in the presence of a catalyst to improve the quality of petrol is referred to as Options:
  A) refining
  B) craching
  C) reforming
  D) blending
  Show Answer
  The correct answer is C .
• Question 447:

  A compound contains 31.91% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formula of the compound?

  [K = 39, Cl = 35.5, O = 16]

  Options:
  A) KClO₄
  B) KClO
  C) KClO₂
  D) KClO₃
  Show Answer
  The correct answer is D .
• Question 448: In the extraction of aluminum from purified bauxite by electrolysis, cryolite is used because Options:
  A) it makes bauxite a better conductor of electricity
  B) it makes bauxite melt at a lower temperature
  C) it makes aluminium purer
  D) it prevents aluminium from getting oxidized
  E) it protects the carbon electrodes used in the process
  Show Answer
  The correct answer is B .
• Question 449: The energy value of petrol can be determined by a Options:
  A) bomb calorimeter
  B) catalytic cracker
  C) fractionating column
  D) thermometer
  Show Answer
  The correct answer is C .
• Question 450: Pure solvents are obtained by Options:
  A) Distillation
  B) Condensation
  C) Extraction
  D) Evaporation
  Show Answer
  The correct answer is A .