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 11:

  What are the possible oxidation numbers of an element if its atomic number is 17?

  Options:
  A) -1 and 7
  B) -1 and 6
  C) -3 and 5
  D) -2 and 6
  Show Answer
  The correct answer is A .
• Question 12: The molar ratio of oxygen to nitrogen in dissolved air is 2:1 whereas the ratio is 4:1 in atmospheric air because? Options:
  A) nitrogen is less soluble than oxygen
  B) oxygen is heavier than nitrogen
  C) nitrogen has a higher partial pressure in air
  D) gases are hydrated in water
  Show Answer
  The correct answer is A .
• Question 13: The shape of s-orbitals is Options:
  A) spherical
  B) elliptical
  C) spiral
  D) circular
  Show Answer
  The correct answer is A .
• Question 14: Which of the following pairs has compounds that are isomers? Options:
  A) Propanal and propanone
  B) Ethanoic acid and ethylmethanoate
  C) Ethanoic acid and ethane-1, 2-diol
  D) 2-methylbutane and 2, 2-dimethylbutane
  Show Answer
  The correct answer is D .
• Question 15: Ammonium chloride can be separated from its mixture with common salt by Options:
  A) Distillation
  B) Evaporation
  C) Decantation
  D) Sublimation
  Show Answer
  The correct answer is D .
• Question 16: A correct electrochemical series can be obtained from K, 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
  E) Au and Hg
  Show Answer
  The correct answer is A .
• Question 17: The knowledge of half-life can be used to Options:
  A) create an element
  B) detect an element
  C) split an element
  D) irradiate an element
  Show Answer
  The correct answer is A .
• Question 18: In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm³ of 1.25 molar sulphuric acid? Options:
  A) 5cm³
  B) 10cm³
  C) 20cm³
  D) 25cm³
  E) 50cm³
  Show Answer
  The correct answer is E .
• Question 19: Which of the following solutions will conduct the least amount of electricity? Options:
  A) 2.00 M aqueous solution of NaOH
  B) 0.01 M aqueous solution of NaOH
  C) 0.01 M aqueous solution of hexanoic acid
  D) 0.01 M aqueous solution of sugar
  Show Answer
  The correct answer is D .
• Question 20: Four elements P,Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively . Which of these electrons is a noble gas? Options:
  A) P
  B) Q
  C) R
  D) S
  Show Answer
  The correct answer is B .