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 831: The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius? Options:
  A) electropositivity decreases from Li to Na to K
  B) electronegativity decreases from Li to Na to K
  C) the number of the electron shells increases from Li to Na to K
  D) the elements are in the same period
  Show Answer
  The correct answer is C .
• Question 832: The difference between colloides and and suspensions is brought out clearly by the fact that while colloids? Options:
  A) do not scatter light, suspensions do
  B) can be separated by filtration, suspension cannot be so separated
  C) can be separated by a membrane, suspensions cannot
  D) do not settle out on standing, suspensions do
  Show Answer
  The correct answer is D .
• Question 833:

  From the graph above, it may be concluded that

  Options:
  A) AgNO${}_3$ is probably not soluble at 1100
  B) NaCl is insoluble in water
  C) Pb(NO${}_3$)${}_2$ is more soluble than KCIO${}_3$
  D) The solubility of KCIO${}_3$ exceeds that of NaCl at all temperature
  Show Answer
  The correct answer is C .
• Question 834: The constituent of air that acts as a diluent is Options:
  A) nitrogen
  B) carbon (IV) oxide
  C) noble gases
  D) oxygen
  Show Answer
  The correct answer is A .
• Question 835:

  An isotope has an atomic number of 15 and a mass number of 31. The number of protons it contains is

  Options:
  A) 16
  B) 15
  C) 46
  D) 31
  Show Answer
  The correct answer is B .
• Question 836: The phenomenon whereby sodium trioxocarbonate (IV) decahydrate loses some of its water of crystallization on exposure to the atmosphere is known as? Options:
  A) deliquescene
  B) hygroscopy
  C) effervescence
  D) efflorescence
  Show Answer
  The correct answer is D .
• Question 837:

  The metal used to recover copper from a solution of copper sulphateis?

  Options:
  A) Na
  B) Ag
  C) Hg
  D) Fe
  Show Answer
  The correct answer is D .
• Question 838:

  The heat required to raise the temperature of the body by 1k is called?

  Options:
  A) Specific heat
  B) Thermal capacity
  C) Water equivalent
  D) None of the above
  Show Answer
  The correct answer is B .
• Question 839:

  CO_(g) + H₂ O_(g) → CO_2(g) + H_2(g)

  Calculate the standard heat change of the reaction above, if the standard enthalpies of formation of CO_2(g), H₂O_(g) and CO_(g) and CO_(g) in KJ mol ^-1 are - 394 -242 and - 110 respectively.

  Options:
  A) + 262 KJ mol ^-1
  B) - 262 KJ mol ^-1
  C) + 42 KJ mol ^-1
  D) - 42 KJ mol ^-1
  Show Answer
  The correct answer is D .
• Question 840: A solution of calcium bromide contains 20 g dm ³ What is the molarity of the solution with respect to calcium bromide and bromide ions? [Ca = 40, Br = 80] Options:
  A) 0. 1, 0 . 1
  B) 0. 1, 0. 2
  C) 0. 1, 0. 05
  D) 0.05, 0.1
  Show Answer
  The correct answer is C .