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:

  What is the maximum number of electrons that can occupy the second energy level (n=2)?

  Options:
  A) 2 electrons
  B) 18 electrons
  C) 8 electrons
  D) 32 electrons
  Show Answer
  The correct answer is C .
• Question 92:

  In which of the following will hydrogen form ionic compound?

  Options:
  A) HCL
  B) NaH
  C) NH${}_3$
  D) CH${}_4$
  Show Answer
  The correct answer is B .
• Question 93: If 100cm³ of oxygen pass through a porous plug is 50 seconds, the time taken for the same volume of hydrogen to pass through the same porous plug is? [O = 16, H = 1] Options:
  A) 10.0s
  B) 12.5s
  C) 17.7s
  D) 32.0s
  Show Answer
  The correct answer is B .
• Question 94: Hardness of water is mainly due to the presence of Options:
  A) calcium hydroxide or magnesium hydroxide
  B) calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI)
  C) sodium hydroxide or magnesium ydroxide
  D) calcium chloride or sodium chloride salts
  Show Answer
  The correct answer is B .
• Question 95: The solubility of a salt of molar mass 101g at 20^oC is 0.34 mol dm^-3. If 3.40g of the salt is dissolved completely in 250cm³ of water in a beaker, the resulting solution is Options:
  A) A suspension
  B) Saturated
  C) Unsaturated
  D) Supersaturated
  Show Answer
  The correct answer is C .
• Question 96:

  Which of the following is an example of a chemical change?

  Options:
  A) dissolution of salt in water
  B) rusting of iron
  C) melting of ice
  D) separating a mixture by distillation
  Show Answer
  The correct answer is B .
• Question 97: A compound contains 40.0% C, 6.7% H 53.3% O. If the molecular mass of the compound is 180, its molecular formula is [C =12, H =1,O] Options:
  A) CH₂O
  B) C₃H₆O₃
  C) C₆H₆O₃
  D) C₆H₁₂O₆
  Show Answer
  The correct answer is D .
• Question 98:

  A chemical process in which there is a gain of electrons is known as?

  Options:
  A) Sublimation
  B) Reduction
  C) Oxidation
  D) Distillation
  Show Answer
  The correct answer is B .
• Question 99:

  What quantity of electricity will liberate 0.125 mole of oxygen molecules during the electrolysis of dilute sodium chloride solution?

  [ F = 96 5000 C mol^-1 ]

  Options:
  A) 24 125 coulombs
  B) 48 250 coulombs
  C) 72 375 coulombs
  D) 96 500 coulombs
  Show Answer
  The correct answer is B .
• Question 100:

  Hard water is water with high concentrations of dissolved ions, in particular calcium and

  Options:
  A) magnesium ions
  B) nitrogen ions
  C) phosporus ions
  D) helium ions
  Show Answer
  The correct answer is A .