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 51:

  What happens to the value of the equilibrium constant (Kc) for a reaction if the reaction is reversed?

  Options:
  A) It becomes zero
  B) It becomes negative
  C) It remains the same
  D) It becomes the reciprocal of the original value
  Show Answer
  The correct answer is D .
• Question 52: Bleaching powder, CaOCI₂, H₂O, deteriorates on exposure to air because Options:
  A) it loses its water of crystallization
  B) atmospheric nitrogen displaces chlorine from it
  C) carbon (IV) oxide of the atmosphere displaceschlorine from it
  D) bleaching agents should be stored in solution
  Show Answer
  The correct answer is C .
• Question 53: In the periodic table, the electrical and thermal conductivities are properties of elements that Options:
  A) decrease across the period and increase down the group
  B) increase across the period and decrease down the group
  C) decrease across the period and down the group`
  D) increase acrosss the period and down the group
  Show Answer
  The correct answer is A .
• Question 54: If one of the following oxides is heated with hydrogen or carbon using a bunsen burner, it is not reduced to the metal. Which one is it? Options:
  A) Lead oxide
  B) Magnesium oxide
  C) Copper oxide
  D) Tin oxide
  E) Iron oxide
  Show Answer
  The correct answer is B .
• Question 55:

  How many atoms are present in 6.0g of magnesium?

  [Mg = 24, N_A = 6.02 x 10²³ mol^-1]

  Options:
  A) 1.20 x 10²²
  B) 2.41 x 10²²
  C) 1.51 x 10²³
  D) 3.02 x 10²³
  Show Answer
  The correct answer is C .
• Question 56: Alkaline hydrolysis of naturally occurring fats and oils yields Options:
  A) fats and acids
  B) soaps and glycerol
  C) margarine and butter
  D) esters
  E) detergents
  Show Answer
  The correct answer is B .
• Question 57: Oxyacetylene flame is used for iron-welding because it Options:
  A) Makes the iron metals solidify very quickly
  B) Combines with oxygen to give a pop sound
  C) Evolves a lot of heat when burnt
  D) Dissociates to produce carbon (IV) oxide and oxygen
  Show Answer
  The correct answer is C .
• Question 58: Reduction of nitroalkanes, nitrites and amides is a route for the preparation of Options:
  A) amines
  B) alkenes
  C) polymers
  D) detergents
  Show Answer
  The correct answer is A .
• Question 59: In an endothermic reaction, if there is a loss in entropy the reaction will Options:
  A) be indeterminate
  B) be spontaneous
  C) not be spontaneous
  D) be at equilibrium
  Show Answer
  The correct answer is C .
• Question 60: Which of the following elements will form oxide which will dissolve both in dilute HNO₃ and NaOH solutions to form salts? Options:
  A) Al
  B) Mg
  C) Ag
  D) Mn
  Show Answer
  The correct answer is A .