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 31: In the electrolysis of CuSo_4(g) using platinum electrode the reaction at the anode is Options:
  A) 4H+ 4e - 2H₂
  B) 4OH^-- 4e = 2H₂O + O₂
  C) 2OH - 2e_- = 2OH
  D) 2OH^- + 2OH = 2H₂O + O₂
  Show Answer
  The correct answer is B .
• Question 32:

  2H${}_2$ + O${}_2$ 2H${}_2$O

  From the equationabove, calculate the volume of unreacted oxygen gas if a mixture of 50cm${}^3$ of hydroden and 75cm${}^3$ of oxygen are involved

  Options:
  A) 85cm${}^3$
  B) 50cm${}^3$
  C) 125cm${}^3$
  D) 55cm${}^3$
  Show Answer
  The correct answer is B .
• Question 33: If chlorine gas is bubbled into water and then this yellowish-green coloured solution is exposed to bright sunlight for a while Options:
  A) the solution will give out chlorine gas and hydrogen chloried gas
  B) the solution will produce chlorine gas and oxygen
  C) the solution will give out solution will producing hypochloric acid
  D) the solution is decomposed giving out oxygen, hydrogen and chlorine
  E) the solution will give out oxygen gas leaving behind aqueous hydrochloric acid
  Show Answer
  The correct answer is E .
• Question 34: The allotropy of carbon used in the decolourization of sugar is Options:
  A) Graphite
  B) Soot
  C) Charcoal
  D) Lampblack
  Show Answer
  The correct answer is C .
• Question 35:

  The two ions responsible for hardness in water are

  Options:
  A) Ca${}^{2+}$ and / or Mg${}^{2+}$
  B) K${}^{+}$ and / or Mg${}^{2+}$
  C) Ca${}^{2+}$ and / or Li${}^{+}$
  D) Ca${}^{2+}$ and / or Na${}^{+}$
  Show Answer
  The correct answer is A .
• Question 36:

  When the end alkyl groups of ethyl ethanoate are interchanged, the compound formed is

  Options:
  A) propylmethanoate
  B) ethylpropanoate
  C) methyl ethanoate
  D) methyl propanoate
  Show Answer
  The correct answer is B .
• Question 37:

  Elements in the periodic table are arranged in the order of their

  Options:
  A) atomic numbers
  B) metallic character
  C) mass number
  D) relative atomic mass
  Show Answer
  The correct answer is A .
• Question 38:

  

  Use the graph above to answer this question.How long does it take all the solid to melt?`

  Options:
  A) 2.5 mins
  B) 6.0 mins
  C) 1.0 min
  D) 3.0 mins
  Show Answer
  The correct answer is A .
• Question 39: The mixture of gases used in a photographer's flash tube is Options:
  A) argon and krypton
  B) krypton and xenon
  C) helium and argon
  D) argon and xenon
  Show Answer
  The correct answer is B .
• Question 40: An organic compound reacted with bromine water to give a colourless solution. The compound is probably an Options:
  A) alkene
  B) alkanal
  C) alkyne
  D) alkanone
  Show Answer
  The correct answer is C .