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: A gas X diffuses twice as fast as gas Y. if the relative molecular mass of X is 32, calculate the relative molecular mass of Y. Options:
  A) 128
  B) 8
  C) 16
  D) 64
  Show Answer
  The correct answer is A .
• Question 1992: Which of the following compounds can exist as geometric isomers? Options:
  A) 2-methylbut-2ene
  B) But-2-ene
  C) But-1-ene
  D) CI-C-Br
  Show Answer
  The correct answer is B .
• Question 1993: A major process involved in the softening of hard water is the? Options:
  A) conversation of a soluble calcium salt to its trioxoncarbonate (lV)
  B) decomposition of calcium rioxocarbonate (lV)
  C) conversion of an insoluble calcium salts to its trioxocarbonate (lV)
  D) oxidation of calcium atoms to its ions
  Show Answer
  The correct answer is A .
• Question 1994: (1 /(2) N_2(g) + (1) / (2)O_2(g) → NO_(g) ∆H° 89 KJ mol^-. If the entropy change for the reaction above at 25°C is 11.8 J mol^-, calculate the change in free energy. ∆G°, for the reaction at 25°C? Options:
  A) 88.71 KJ
  B) 85.48 KJ
  C) -204.00 KJ
  D) -3427.40 KJ
  Show Answer
  The correct answer is D .
• Question 1995: The reddish–brown rust on ion roofing sheets consists of Options:
  A) Fe³ + (H₂O)₆
  B) FeO.H₂O
  C) Fe₂O₃.3H₂O
  D) Fe₃O₄.2H2₂O
  Show Answer
  The correct answer is C .
• Question 1996:

  

  The tabulated results below were obtained by titration 10.0 cm³ of water with soup. The titration was repeated with the same sample of water after boiling. The ratio of permanent to temporary hardness is

  Options:
  A) 1.5
  B) 1.4
  C) 4.1
  D) 5.1
  Show Answer
  The correct answer is C .
• Question 1997: Sodium carbonate crystals on exposure to a dry atmosphere change to a white powder. This phenomenon is known as? Options:
  A) deliquescence
  B) hygroscopy
  C) oxidation
  D) efforescence
  E) sublimation
  Show Answer
  The correct answer is D .
• Question 1998:

  

  The IUPAC nomenclature for the compound above is

  Options:
  A) dimethlhexane
  B) 3,5 dimethylhexane
  C) 1.1 dmethyl, 3 methylpentane
  D) 2.4 dimethylhexane
  Show Answer
  The correct answer is D .
• Question 1999: A solution containing chloride ions gives white precipitate with silver trioxonitrate(V) Solution. The precipitate will be insoluble in dilute? Options:
  A) HNO ₃ but soluble in ammonia solution
  B) HNO₃ and ammonia solution
  C) HCl but soluble in ammonia solution
  D) HCl and in ammonia solution
  Show Answer
  The correct answer is A .
• Question 2000: The nitrogen gas obtained by burning an excess of phosphorus in air has a density higher than the nitrogen from nitrogen compounds because the nitrogen from air is contaminated with? Options:
  A) some unburnt phosporus
  B) P₂O₅ vapour
  C) some oxygen
  D) rare gases
  E) carbondioxide
  Show Answer
  The correct answer is D .