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 1021: In recharging a lead-acid accumulator, the reaction at the cathode can be represented as Options:
  A) Pb²⁺_(aq) + SO^2-_4(aq) →PbSO_4(s)
  B) Pb²⁺_(aq) + 2e^- →Pb_(s)
  C) Pb²⁺_(aq) + 2H₂O_(l) → PbO_2(s) + 4H⁺_(aq) + 4e^-
  D) Pb_(s) → Pb²⁺_(aq) + 2e^-
  Show Answer
  The correct answer is D .
• Question 1022:

  Which of the compounds is composed of Al, Si, O and H?

  Options:
  A) Epson salt
  B) Limestone
  C) Clay
  D) Urea
  Show Answer
  The correct answer is C .
• Question 1023: The most abundant element on the earth's crust is Options:
  A) nitrogen
  B) hydrogen
  C) oxygen
  D) flourine
  Show Answer
  The correct answer is C .
• Question 1024: In which of the following is the entropy change positive? Options:
  A) H₂O_(I) → H₂O_(g)
  B) Cu²⁺_{(aq) + Fe(s)} → Fe⁽²⁺⁾ + Cu_(s)
  C) N_2(g) + 3H_2(g) → 2NH_3(g)
  D) 2HCI_(s) → H_2(g) + CI_2(g)
  Show Answer
  The correct answer is A .
• Question 1025:

  A correct electrochemical series can be obtained from Na, Ca, Al, Mg, Zn, Fe, Pb, H, Cu, Hg, Ag, Au by interchanging

  Options:
  A) Al and Mg
  B) Zn and Fe
  C) Zn and Pb
  D) Pb and H
  Show Answer
  The correct answer is A .
• Question 1026: Alkanals can be differentiated from alkanones by reaction with? Options:
  A) 2,4-dinitrophenylhydrazine
  B) hydrogen cyanide
  C) sodium hydrogen sulphite
  D) Tollen's reagent
  Show Answer
  The correct answer is D .
• Question 1027:

  GAS	CO${}_2$	N${}_2$	O${}_2$
  % BY VOLUME	4	72	24

  The above table shows the compositions of the atmosphere of planet X. Which of these gases are present inhigherpercentages on earth?

  Options:
  A) CO${}_2$ and O${}_2$
  B) N${}_2$ and CO${}_2$
  C) CO${}_2$, O${}_2$ and N${}_2$
  D) O${}_2$ and N${}_2$
  Show Answer
  The correct answer is D .
• Question 1028: Hardness of water is mainly due to the presence of Options:
  A) calcium hydroxide or magnesium hydroxide
  B) calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI)
  C) sodium hydroxide or magnesium ydroxide
  D) calcium chloride or sodium chloride salts
  Show Answer
  The correct answer is B .
• Question 1029: In the electrolysis of brine the anode is Options:
  A) platinum
  B) copper
  C) zinc
  D) carbon
  Show Answer
  The correct answer is D .
• Question 1030: Which of the following substances are all made by the process of polymerization? Options:
  A) Nylon and soap
  B) Ethanoic acid margarine and ethanol
  C) Nylon and artificial rubber
  D) Soap and butane
  E) Margarine and nylon
  Show Answer
  The correct answer is C .