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 1541: On exposure to the atmosphere, a hydrated salt loses its water of crystallization to become anhydrous. This phenomenon is referred to as Options:
  A) efflorescence
  B) diliquescence
  C) hygroscopy
  D) hydrolysis
  Show Answer
  The correct answer is A .
• Question 1542: A red precipitate of copper (I) carbide is formed when ammonium solution of copper (I) chloride is introduced into Options:
  A) CH₂ = CH - CH₂ - CH₃
  B) CH₃ CH₂ - C ≡ CH
  C) CH₃ CH₂ CH₂ CH₃
  D) CH₃ - C C - CH₃
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  The correct answer is B .
• Question 1543: Chlorination of water for town supply is carried out to Options:
  A) make the water colourless
  B) remove germs from the water
  C) make the water tastedful
  D) remove odour from the water
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  The correct answer is B .
• Question 1544: If chlorine is bubbled into water and the resulting yellowish-green solution is exposed to bright sunlight for a while, the solution will decompose giving out Options:
  A) oxygen and leaving behind aqueous hydrochloric acid
  B) chlorine and oxygen
  C) oxygen, hydrogen and chlorine
  D) oxygen, thereby producing hypochlorous acid
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  The correct answer is A .
• Question 1545: The haloalkanes used in dry-cleaning industries are Options:
  A) trichloromethane and tetrachloromethane
  B) chloroethene and dichloroethene
  C) trichloroethene and tetrachloroethene
  D) chloroethane and dichloroethene
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  The correct answer is A .
• Question 1546: The products of the thermal decomposition of ammonium trioxonitrate (V) are Options:
  A) NO ₂ and oxygen
  B) NH₃ and oxygen
  C) nitrogen and water
  D) N₂O and water
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  The correct answer is D .
• Question 1547: If the change in free energy of a system is -899 Jmol^-1 and the entropy change is 10Jmol^-1k^-1 at 250C, calculate the enthalpy change. Options:
  A) +2081 Jmol^-1
  B) -2081 Jmol^-1
  C) -649 Jmol^-1
  D) +649 Jmol^-1
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  The correct answer is A .
• Question 1548: Given the reactions (i) Fe_(s) + X(NO₃)_2(aq) → Fe(NO₃) + X_(s) (ii) H_2(g) + XO _{→ X + H2}O_(s); X is likely to be?
  Options:
  A) copper
  B) zinc
  C) calcium
  D) lead
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  The correct answer is A .
• Question 1549:

  The hybridization in the compound $C{H}_3-C{H}_2-C\equiv H$ is

  Options:
  A) sp${}^3$ and sp
  B) sp
  C) sp${}^2$
  D) sp${}^3$ and sp${}^2$
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  The correct answer is A .
• Question 1550: The hydroxyl ion concentrated, (OH^-), in a solution of sodium hydroxide of pH 10.0 is? Options:
  A) 10^-10 mol dm^-3
  B) 10^-6 mol dm^-3
  C) 10^-4 mol dm^-3
  D) 10^-2 mol dm^-3
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  The correct answer is C .