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 931: Addition of dilute hydrochloride acid to an aqueous solution of a crystalline salt yield a yellow precipitate and a gas which turned dichromate paper green. The crystalline salt was probably? Options:
  A) Na₂SO₄
  B) Na₂S
  C) Na₂S₂O₃.5H₂O
  D) Na₂CO₃
  E) NaHCO₃
  Show Answer
  The correct answer is C .
• Question 932: The stability of the noble gases is due to the fact that they Options:
  A) have no electron in their outermost shells
  B) have duplet or octet electron configurations
  C) belong to group zero of the periodic table
  D) are volatile in nature
  Show Answer
  The correct answer is B .
• Question 933: When at equilibrium, which of the reactions below will shift to the right if the pressure is increased and the temperature is kept constant? Options:
  A) 2SO_3(g) ↔ 2SO_2(g) + O_2(g)
  B) 2CO_2(g) ↔ 2CO_(g) + O_2(g)
  C) 2H_2(g) + O_2(g) ↔ 2H₂O_(g)
  D) 2NO_(g) ↔ N_2(g) + O_2(g)
  Show Answer
  The correct answer is C .
• Question 934:

  What is the chemical formula of rust, which is formed on the surface of iron in the presence of oxygen and moisture?

  Options:
  A) Fe${}_3$O${}_4$
  B) FeO
  C) Fe(OH)3
  D) Fe${}_2$O${}_3$
  Show Answer
  The correct answer is D .
• Question 935:

  When heat is absorbed during a chemical reaction, the reaction is said to be

  Options:
  A) thermodynamic
  B) exothermic
  C) isothermal
  D) endothermic
  Show Answer
  The correct answer is D .
• Question 936: Sieving is a technique used to separate mixtures containing solid particles of Options:
  A) small sizes
  B) large sizes
  C) different sizes
  D) the same size
  Show Answer
  The correct answer is C .
• Question 937: Which of the following is NOT true of metals? Options:
  A) They are good conductors of electricity
  B) They ionize by electron loss
  C) Their oxides are acidic
  D) They have high melting points
  Show Answer
  The correct answer is C .
• Question 938: In which of the following is the entropy change positive? Options:
  A) H₂O_(I) → H₂O_(g)
  B) Cu²⁺_{(aq) + Fe(s)} → Fe⁽²⁺⁾ + Cu_(s)
  C) N_2(g) + 3H_2(g) → 2NH_3(g)
  D) 2HCI_(s) → H_2(g) + CI_2(g)
  Show Answer
  The correct answer is A .
• Question 939: Haematite is an ore of Options:
  A) zinc
  B) lead
  C) iron
  D) copper
  Show Answer
  The correct answer is C .
• Question 940: The oxidation state of chlorine in potassium chlorate is Options:
  A) +1
  B) +2
  C) +3
  D) +5
  E) +7
  Show Answer
  The correct answer is D .