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 791: The number of atoms in one mole of a substance is equal to? Options:
  A) the atomic number
  B) the avogadro number
  C) the gas constant
  D) the number of neutrons
  E) the number of electrons
  Show Answer
  The correct answer is B .
• Question 792:

  When 10g of sodium hydroxide is dissolved in 1000cm³ of water, the sodium formed is approximately

  [Na = 23, H = 1, O = 16]

  Options:
  A) 0.01 mol dm^-3
  B) 0.10 mol dm^-3
  C) 0.25 mol dm^-3
  D) 0.50 mol dm^-3
  Show Answer
  The correct answer is C .
• Question 793:

  Sodium sulphate decahydrate (Na₂SO₄.10 H₂O) on exposure to air loses all its water of crystallization.

  The process of loss is known as

  Options:
  A) efflorescence
  B) hygroscopy
  C) deliquescence
  D) effervescence
  E) dehydration
  Show Answer
  The correct answer is A .
• Question 794:

  What is the mass (in grams) of 500 mL of ethanol? (density of ethanol = 0.789 g/mL)

  Options:
  A) 394.5 mL
  B) 500 mL
  C) 394.5 g
  D) 500 g
  Show Answer
  The correct answer is C .
• Question 795:

  Given that M is the mass of a substance deposited during electrolysis and Q is the quantity of electricity consumed, then Faraday's first law can be written as

  [Electrochemical equivalent]

  Options:
  A) M = E/Q
  B) M = EQ
  C) M = Q/E
  D) M = E/2Q
  Show Answer
  The correct answer is B .
• Question 796:

  A small quantity of solid ammonium chloride (NH₄Cl) was heated gently in a test tube, the solid gradually disappears to produce two gases. Later, a white cloudy deposit was observed on the cooler part of the test tube. The ammonium chloride is said to have undergone

  Options:
  A) distillation
  B) sublimation
  C) precipitation
  D) evaporation
  E) decomposition
  Show Answer
  The correct answer is B .
• Question 797:

  I. It has a varied composition from one place to another.

  II. It constituents can be separated by physical means.

  III. It contains unreactive noble gases

  Which of the above shows that air is a mixture?

  Options:
  A) I and II only
  B) II and III only
  C) I and III only
  D) I, II and III
  Show Answer
  The correct answer is A .
• Question 798: POlyvinyl chloride is used to produce Options:
  A) bread
  B) pencils
  C) ink
  D) pipes
  Show Answer
  The correct answer is D .
• Question 799:

  When chlorine water is exposed to bright sunlight, the following products are formed

  Options:
  A) HCl${}_{(aq)}$ and Cl${}_2$
  B) HOCl${}_{(aq)}$ and Cl${}_2$
  C) HCl${}_{(aq)}$ and O${}_2$
  D) HOCl${}_{(aq)}$ and O${}_2$
  Show Answer
  The correct answer is C .
• Question 800: the elements that belong to the third period of the periodic table are Options:
  A) Li, Be, Al and P
  B) Na, P, O and Cl
  C) B, C, N and O
  D) Nz, Mg, S and Ar
  Show Answer
  The correct answer is D .