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 301: The density of a certain gas is 1.98gdm^-3 at s.t.p. What is the molecular mas of the gas? Options:
  A) 44.0 g
  B) 54.0 g
  C) 26.0 g
  D) 31.0 g
  Show Answer
  The correct answer is A .
• Question 302: The modern process of manufacturing steel for iron is by Options:
  A) treatment with acids
  B) oxidation
  C) blast reduction
  D) treatment with alkanal
  Show Answer
  The correct answer is C .
• Question 303: Which of the following processes leads to increase in entropy? Options:
  A) Mixing a sample of NaCl and sand
  B) Condensation of water vapour
  C) Boiling a sample of water
  D) Cooling a saturated solution
  Show Answer
  The correct answer is C .
• Question 304:

  Temp (°C)	25	35	45
  Time (seconds)	72	36	18

  The times taken for iodine to be liberated in the reaction between sodium thiosulphate and hydrochloric acid at various temperature are as follows. These results suggest that

  Options:
  A) for a 10^o rise in temperature, rate of reaction is double
  B) for a 10 ^o rise in temperature, rate of reaction is halved
  C) time taken for iodine to appear does not depend on temperature
  D) for a 10 ^o rise in temperature rate of reaction is tripled
  Show Answer
  The correct answer is A .
• Question 305: During the vulcanization of rubber, sulphur is added to Options:
  A) Break down rubber polymer
  B) Lengthen the chain of rubber
  C) Bind rubber molecules together
  D) Act as a catalyst
  Show Answer
  The correct answer is C .
• Question 306:

  The general formula of alkanoates is?

  Options:
  A) $RCHO$
  B) $R_{2}CO$
  C) $RCOOH$
  D) $RCOO{R}^{\prime }$
  Show Answer
  The correct answer is D .
• Question 307: A major source of oxide of oxygen is from the burning of Options:
  A) coal
  B) wood
  C) fuel
  D) chlorofluorocarbons
  Show Answer
  The correct answer is A .
• Question 308: Which of the following shows little or no net reaction when the volume of the system is decreased? Options:
  A) H_2(g) + I_2(g) ↔ 2HI_(g)
  B) 2NO_2(g) ↔ N₂O_4(g)
  C) PCl_5(g) ↔ PCl_3(g) + Cl_2(g)
  D) 2O_3(g) ↔ 3O_2(g)
  Show Answer
  The correct answer is A .
• Question 309: Which of the following tests would confirm-unequivocally that a solution X contain the sulphate ion if it gives with Options:
  A) silver nitrates solution, a white precipates insoluble in dilute HNO₃
  B) barium chloride solution, a white precipitate insoluble in dilute H₂SO₄
  C) barium chloride solution, a white precipitate insoluble in dilute HCl
  D) barium chloride solution a white precipitate soluble in dilute ammonia
  E) barium chloride solution a white precipitate insoluble in dilute HCl
  Show Answer
  The correct answer is C .
• Question 310: If an element X of an atomic number Z and mass number Y is irradiated by an intense concentration of neutrons, the relevant nuclear equation is? Options:
  A) ^y_zX + ¹₀n → ^{y - 1}_{z + 1}X
  B) ^y_zX + ¹₀n → ^{y + 1}_zX
  C) ^y_zX + ¹₀n → ^y_{z + 1}X
  D) ^y_zX + ¹₀n → ^{y + 1}_{z - 1}X
  Show Answer
  The correct answer is B .