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 91: Calculate the number of moles of HCl present in 20cm³ of a 0.75M solution of the acid Options:
  A) 0.015 mole
  B) 0.038 mole
  C) 3.800 moles
  D) 1.500 moles
  Show Answer
  The correct answer is A .
• Question 92: A sample of an oxide of mercury weighed 1.00g. When this was heated, oxygen was given off, and 1.00g of mercury metal only was left. What is the formula of the oxide? Options:
  A) Hg₂O
  B) HgO₂
  C) HgO₂
  D) HgO
  E) None of the above
  Show Answer
  The correct answer is E .
• Question 93:

  2KClO3(g) MNO3→ 2KCl(s) + 3O2(g)

  The importance of the catalyst in the reaction above is that

  Options:
  A) heating may not be required before the reaction takes place
  B) the reaction is controllable even at a high temperature
  C) the reaction produces large quantity of oxygen
  D) the reaction takes place more rapidly at a lower temperature
  Show Answer
  The correct answer is D .
• Question 94: When sodium ethanoate is treated with a few drops of concentrated tetraoxosulphate(vi)acid. one of the products is Options:
  A) CH₃COOH
  B) CH₃COOCH₃
  C) CH₃COOC₂H₅
  D) C₂H₅COOCH₃
  Show Answer
  The correct answer is A .
• Question 95: A saturated solution of AgCl was found to have a concentration of 1.30 x 10^-5 mol dm^-3. The solubility product of AgCl therefore is? Options:
  A) 1.30 x 10^-5 mol₂ dm^-6
  B) 1.30 x 10^-7 mol₂ dm^-6
  C) 1.69 x 10^-10 mol₂ dm^-6
  D) 2.60 x 10^-12 mol₂ dm^-6
  Show Answer
  The correct answer is C .
• Question 96:

  

  From the diagram above, find the amount of solute deposited when 200 cm³ of the solution is cooled from 55^oC to 40^oC

  Options:
  A) 0.10 mole
  B) 0.20mole
  C) 0.01 mole
  D) 0.02 mole
  Show Answer
  The correct answer is B .
• Question 97:

  Cr₂O₇ + 6Fe²⁺ + 14H⁺ → 2Cr3+ + 6Fe³⁺ + 7H₂O. In the above, the oxidation number of chromium changed from?

  Options:
  A) +7 to +3
  B) +6 to +3
  C) +5 to +3
  D) -2 to +3
  Show Answer
  The correct answer is A .
• Question 98:

  

  The I.U.P.A.C name for the compound

  Options:
  A) 2-chloro-isopentane
  B) 3-chloro-isopentane
  C) 2-chloro-2-methylbutane
  D) 1-chloro-2,2- dimethylpropane
  E) 2-chloro-2-ethylpropane
  Show Answer
  The correct answer is C .
• Question 99: Copper is displaced from the solution of its salts by most metals because it Options:
  A) is a transition element
  B) is at the bottom of the activity series
  C) is very reactive
  D) has completely filled 3d-orbitals
  Show Answer
  The correct answer is B .
• Question 100: The general formula of an alkyl halide (which represent the halide) is? Options:
  A) C_nH_2n - ₂X
  B) C_nH_2n + ₁X
  C) C_nH_2n + ₂X
  D) C_nH_2nX
  E) C_nH_2n - 1
  Show Answer
  The correct answer is B .