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 361:

  Consider the equation below:

  Cr${}_2$O${}_7^{2-}$ + 6Fe${}^{2+}$ + 14H${}^{+}$ $\to$ 2Cr${}^{3+}$ + 6Fe${}^{3+}$ + 7H${}_2$O.

  The oxidation number of chromium changes from

  Options:
  A) +5 to +3
  B) +6 to +3
  C) -2 to +3
  D) +7 to +3
  Show Answer
  The correct answer is B .
• Question 362:

  A certain hydrocarbon on complete combustion at s.t.p produced 89.6dm${}^3$ of CO${}_2$ and 54g of water. The hydrocarbon should be

  Options:
  A) C${}_6$H${}_6$
  B) C${}_4$H${}_{10}$
  C) C${}_5$H${}_{10}$
  D) C${}_4$H${}_6$
  Show Answer
  The correct answer is D .
• Question 363: The tincture of iodine means iodine dissolved in Options:
  A) ethanol
  B) bromine chloride
  C) chlorine water
  D) water
  Show Answer
  The correct answer is A .
• Question 364: When a little brine was added to a metal nitrate a white precipitate was formed which first turned violet and then black on exposure to ai. The metal nitrate is therefore? Options:
  A) sodium nitrate
  B) mercuric nitrate
  C) lithium nitrate
  D) silver nitrate
  E) potassium nitrate
  Show Answer
  The correct answer is D .
• Question 365:

  Calculate the percentage by mass of nitrogen in calcium trioxonitrate (V).
  [Ca = 40, N = 14, O = 16]

  Options:
  A) 8.5%
  B) 13.1%
  C) 17.1%
  D) 27.6%
  Show Answer
  The correct answer is C .
• Question 366: How many Faraday of electricity are required to deposit 0.20 mole of nickel, if 0.10 Faraday of electricity deposited 2.98g of nickel during electrolysis of its aqueous solution?(Ni = 58.7, 1F = 96 500 C mol^-) Options:
  A) 0.20
  B) 0.30
  C) 0.40
  D) 0.50
  Show Answer
  The correct answer is C .
• Question 367:

  N₂O_4(aq) $\rightleftharpoons$ 2NO_2(g) $△$H = +ve

  In the reaction above, an increase in temperature will

  Options:
  A) Increase the reactant production
  B) Increase the value of the equilibrium constant
  C) Shift the equilibrium to the left
  D) Decrease the value of the equilibrium constant
  Show Answer
  The correct answer is B .
• Question 368: Which of the following metals is passive to concentrated trioxonitrate (V) acid? Options:
  A) Iron
  B) Tin
  C) Copper
  D) Zinc
  Show Answer
  The correct answer is A .
• Question 369:

  What is the state of matter in which particles are widely spaced and move freely with high kinetic energy?

  Options:
  A) Liquid
  B) Solid
  C) Plasma
  D) Gas
  Show Answer
  The correct answer is D .
• Question 370: A difference between chemical and physical change is that in a chemical change Options:
  A) oxygen is consumed
  B) heat is supplied
  C) the reversible process occurs
  D) a new substance is formed
  Show Answer
  The correct answer is D .