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 1131:

  CH₂S_(g) + O_2(g) → 2Cn + SO_2(g)

  What is the change in the oxidation number of copper in the reaction?

  Options:
  A) 0 to + 2
  B) 0 to + 1
  C) C + 1 to 0
  D) + 2 to + 1
  Show Answer
  The correct answer is C .
• Question 1132: The number of hydroxonium ions produced by one molecule of an acid in aqueous solution is its Options:
  A) basicity
  B) acid strength
  C) pH
  D) concentration
  Show Answer
  The correct answer is B .
• Question 1133:

  What happens to the position of equilibrium, if a reversible exothermic reaction is subjected to a decrease in temperature?

  Options:
  A) The position of equilibrium shifts to the left
  B) The position of equilibrium shifts to the right.
  C) The position of equilibrium remains unchanged
  D) The reaction stops
  Show Answer
  The correct answer is B .
• Question 1134: 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 1135: Calculate the amount in moles of silver deposited when 9650C of electricty is passed through a solution of silver salt [= 96500 Cmol^-1] Options:
  A) 0.05
  B) 10.80
  C) 10.00
  D) 0.10
  Show Answer
  The correct answer is D .
• Question 1136:

  Calculate the volume in cm³ of oxygen evolved as s.t.p. when a current of 5 A is passed through acidified water for 193s

  {F = 96500 Cmol^-1, Molar volume of a gas at s.t.p. = 22.4 dm³}

  Options:
  A) 224.000 dm³
  B) 0.056 dm³
  C) 0.224 dm³
  D) 56.000 dm³
  Show Answer
  The correct answer is B .
• Question 1137: The iron (III) oxide impurity in bauxite can be removed by? Options:
  A) Fractional crystallization in acid solution
  B) dissolution in sodium hydroxide and filtration
  C) extraction with concentrated ammonia and reprecipitation
  D) electroysis of molten mixture
  Show Answer
  The correct answer is B .
• Question 1138: 35 cm³ of hydrogen was sparked with 12 cm³ of oxygen at 110°C and 760mm Hg to produce steam. What percentage of the total volume of gas left after the reaction is hydrogen? Options:
  A) 11%
  B) 31%
  C) 35%
  D) 69%
  Show Answer
  The correct answer is B .
• Question 1139: The impurities formed during the laboratory preparation of chlorine gas are removed by Options:
  A) H₂O
  B) NH₃
  C) H₂SO₄
  D) HCl
  Show Answer
  The correct answer is A .
• Question 1140:

  Which group does calcium belong to in the periodic table?

  Options:
  A) Alkaline earth metals
  B) Halogens
  C) Alkali metals
  D) Noble gases
  Show Answer
  The correct answer is A .