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 2131: A phenomenon where an element exist in different forms in the same physical state is known as Options:
  A) isomerism
  B) amorphism
  C) allotropy
  D) isotopy
  Show Answer
  The correct answer is C .
• Question 2132: Phosphorus is stored under water to prevent it from Options:
  A) Dehydrating
  B) Becoming inert
  C) Smelling
  D) Catching fire
  Show Answer
  The correct answer is D .
• Question 2133: The chlorinated alkane often used industrially to remove grease is Options:
  A) tetrachloromethane
  B) chloromethane
  C) trichloromethane
  D) dichlorometane
  Show Answer
  The correct answer is A .
• Question 2134: A compound contains 40.0% C, 6.7% H 53.3% O. If the molecular mass of the compound is 180, its molecular formula is [C =12, H =1,O] Options:
  A) CH₂O
  B) C₃H₆O₃
  C) C₆H₆O₃
  D) C₆H₁₂O₆
  Show Answer
  The correct answer is D .
• Question 2135: Lime - water, which is used in the laboratory for the detection of carbon(iv)oxide is an aqueous solution of Options:
  A) Ca(OH)₂
  B) CaCO₃
  C) CaHCO₃
  D) CaSO₄
  E) N₂CO₃
  Show Answer
  The correct answer is A .
• Question 2136: Which of the following salts can be melted without decomposition? Options:
  A) Na₂CO₃
  B) CaCO₃
  C) MgCO₃
  D) ZnCO₃
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  The correct answer is A .
• Question 2137:

  To obtain pure carbon(ii)oxide from its mixture with carbon(iv)oxide, the mixture should be?

  Options:
  A) Passed over heated copper(ii)oxide
  B) Bubbled through water
  C) Bubbled through conc H${}_2$SO${}_4$
  D) Bubbled through conc NAOH
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  The correct answer is D .
• Question 2138:

  Al₂O_3(s) + 3H₂SO_4(aq) → Al₂(SO_4(aq)) + 3H_2(I)O

  Al₂O_3(s) + 2NaOH_(aq)) + 3H_2(I)O → 2NaAl(OH)_4(aq)).

  We can conclude from the equations above that Al₂O_3(s) is?

  Options:
  A) an acidic oxide
  B) an amphoteric oxide
  C) a basic oxide
  D) a neutral oxide
  Show Answer
  The correct answer is B .
• Question 2139:

  In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will

  Options:
  A) be very reactive and will attack ozone
  B) be non-reactive and will not attack ozone
  C) not change the level of ozone in the atmosphere
  D) increase the level of ozone in the atmosphere
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  The correct answer is A .
• Question 2140: A little quantity of trichloromethane (b.pt 60,^oC) was added to a large quantity of ethanol (b.pt 78,^oC). The most probable boiling point of the resultant mixture is from Options:
  A) 69 ^oC - 70 ^oC
  B) 70 ^oC – 74 ^oC
  C) 82 ^oC – 84 ^oC
  D) 60 ^oC – 78 ^oC
  Show Answer
  The correct answer is C .