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 1991: One mole of a hydrocarbon contains 36g of carbon and its vapour density is 20. The structure of the hydrocarbon is Options:
  A) CH₃C ≡ CH
  B) CH₃CH = CH₂
  C) CH₃CH₂C ≡ CH
  D) CH₃CH₂ CH₃
  Show Answer
  The correct answer is A .
• Question 1992: The entropy and enthalpy of a system are a measure of Options:
  A) degree of disorderlinesss and heat content respectively
  B) heat content and degree of disorderliness respectively
  C) heat content of a system only
  D) degree of disorderliness only
  Show Answer
  The correct answer is A .
• Question 1993: One mole of propane is mixed with five moles of oxygen. The mixture is ignited and the propane burns completely. What is the volume of the products at s.t.p?(G.M.V = 22.4 dm³ mol^-1) Options:
  A) 112.0 dm³
  B) 67.2 dm³
  C) 56.0 dm³
  D) 44.8 dm³
  Show Answer
  The correct answer is B .
• Question 1994: What volume of oxygen will remain after reacting 8cm³ of hydrogen with 20cm³ of oxygen? Options:
  A) 10 cm³
  B) 12 cm³
  C) 14 cm³
  D) 16 cm³
  Show Answer
  The correct answer is D .
• Question 1995: If 30cm³ of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm³ of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively? Options:
  A) 9.3 sec
  B) 14 sec
  C) 21 sec
  D) 28 sec
  E) 30.3 sec
  Show Answer
  The correct answer is C .
• Question 1996:

  P_(g) + Q_(g) ↔ 3R_(s) + S_(g) ΔH is negative

  Which of the following will increase the yield of R?

  Options:
  A) Using a larger close vessel
  B) Increasing the temperature
  C) Removing some S
  D) Adding a positive catalyst
  Show Answer
  The correct answer is C .
• Question 1997: On heating, which of the following compounds will decompose to the free metal, nitrogen (IV) oxide and oxygen? Options:
  A) Ca(NO₃)₂
  B) Cu(NO₃)₂
  C) AgNO₃
  D) NaNO₃
  Show Answer
  The correct answer is C .
• Question 1998: In which of the following reactions is sulphur dioxide acting as an oxidizing agent? Options:
  A) SO ₂ + 2HNO₃ →H₂SO₄ + NO₂ + Heat
  B) 2SO₂ + 2H₂O + O₂→ 2H₂SO₄
  C) SO₂ + 2H₂O + CI₂→ H₂SO₄ + 2HCI
  D) SO₂ + 2H₂S → 3S + 2H₂O
  E) SO₂ + H₂O → H₂SO₃
  Show Answer
  The correct answer is D .
• Question 1999: For a given solute, the concentration of its saturated solution in different solvents are Options:
  A) the same at the same temperature
  B) different at the same temperature
  C) the same at different temperature
  D) constant
  Show Answer
  The correct answer is B .
• Question 2000: 2SO_2(g) + O_2(g) 2SO₃. In the reaction above, the standard heats of formation of SO_2(g) and SO_3(g) are -297 KJ mol^-1 respectively. The heat change of the reaction is? Options:
  A) -99 kJ mol^-
  B) -198 kJ mol^-
  C) +198 kJ mol^-
  D) +683kJ mol^-
  Show Answer
  The correct answer is B .