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 621:

  An element, X, forms a volatile hydride XH₃ with a vapour density of 17.0. The relative atomic mass of X is?

  (H = 1)

  Options:
  A) 34.0
  B) 31.0
  C) 20.0
  D) 14.0
  Show Answer
  The correct answer is B .
• Question 622:

  ¹⁴₆C → X + B

  X in the equation above represents

  Options:
  A) ¹²₆C
  B) ¹²₅B
  C) ¹⁴₇N
  D) ¹³₆C
  Show Answer
  The correct answer is C .
• Question 623:

  How many pi ($\pi$) bonds are there in an alkene with six carbon atoms?

  Options:
  A) 4
  B) 6
  C) 5
  D) 3
  Show Answer
  The correct answer is D .
• Question 624:

  X is a substance which liberates CO${}_2$ on treatment with concentrated H${}_2$SO${}_4$. A warm solution of X can decolorize acidified KMnO${}_4$. X is

  Options:
  A) HCOOH
  B) NaHCO${}_3$
  C) FeCO${}_3$
  D) H${}_2$C${}_2$O${}_4$
  Show Answer
  The correct answer is D .
• Question 625:

  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 626: The leachate of a certain ash is used in local soap because it contain Options:
  A) sodium chloride and potassium hydroxide
  B) sodium hydroxide
  C) potassium hydroxide
  D) soluble carbonates and hydrogen carbonate
  Show Answer
  The correct answer is B .
• Question 627: Calculate the mass, in kilograms, of magnesium produced by the electrolysis of magnesium (II) chloride in a cell operating for 24 hours at 500 amperes. Options:
  A) 2.7
  B) 5.4
  C) 10.8
  D) 21.7
  Show Answer
  The correct answer is B .
• Question 628: The impurities formed during the laboratory preparation of chlorine gas are removed by Options:
  A) H₂O
  B) NH₃
  C) H₂SO₄
  D) HCl
  Show Answer
  The correct answer is A .
• Question 629: How many isomers does pentane have? Options:
  A) 6
  B) 5
  C) 4
  D) 3
  Show Answer
  The correct answer is D .
• Question 630:

  A cell shorthand notation can be written as A / A${}^{+}$ // B${}^{2+}$ /B. The double slash in the notation represents the 

  Options:
  A) electrolyte
  B) electrodes
  C) salt bridge
  D) solid - liquid interface
  Show Answer
  The correct answer is C .