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 1851: A gas jar was inverted over burning yellow phosphorus floating over water in a beaker. After burning, the water level was found to rise in the gas jar. The water level rises because Options:
  A) pressure inside the gas jar is greater than pressure outside it
  B) the air in the gas jar had been used up by burning
  C) oxygen in the gas jar had been used up by burning
  D) nitrogen in the gas jar had been used up by burning
  E) the temperature in the jar had risen considerably
  Show Answer
  The correct answer is C .
• Question 1852: The following arrangement of elements in order of decreasing number of outer electrons; One of the elements is wrongly placed. Which is it? ALUMINIUM, CHLORINE, SILICON, MAGNESIUM AND SODIUM. Options:
  A) chlorine
  B) aluminium
  C) silicon
  D) magnesium
  E) sodium
  Show Answer
  The correct answer is B .
• Question 1853:

  

  Z in diagram above represents

  Options:
  A) heat of reaction
  B) activation energy
  C) free energy
  D) entropy of reaction
  Show Answer
  The correct answer is A .
• Question 1854: The brown coloration in nitric acid prepared in the laboratory can be removed by? Options:
  A) heating the acid
  B) bubbling air through the acid
  C) cooling the acid
  D) adding a decolorizing agent
  E) adding a base
  Show Answer
  The correct answer is B .
• Question 1855: Which of the following compounds is composed of Al, Si, O and H? Options:
  A) Epsom salt
  B) Limestone
  C) Clay
  D) Urea
  Show Answer
  The correct answer is C .
• Question 1856: Sulphur (IV)oxide is a strong reducing agent in the presence of water due to the formation of Options:
  A) hydroxide ion
  B) sulpgur (Vl)oxide
  C) hydrogen sulhide
  D) trioxosulphate (IV) salt
  Show Answer
  The correct answer is D .
• Question 1857: Which of the following combinations of conditions may increase the rate of a chemical reaction? Options:
  A) Decrease in temperature, increase in concentration of the reactants
  B) Increase in temperature, addition of a catalyst, decrease in the surface area of the reactants
  C) Increase in temperature, increase in concentration, addition of a catalyst and increase in the surface area of the reactants
  D) Decrease in temperature concentration and surface area of the reactants
  E) Additionof a catalyst and in the absence of light
  Show Answer
  The correct answer is C .
• Question 1858: What is the oxidation number of Z in K₃ZCl₆? Options:
  A) -3
  B) +3
  C) -6
  D) +6
  Show Answer
  The correct answer is B .
• Question 1859:

  Liquid black soap is made by boiling palm oil with liquid extract of ash. The function of the ash is to provide the

  Options:
  A) Acid
  B) Ester of alkanoic acid
  C) Alkali
  D) Alkanol
  Show Answer
  The correct answer is C .
• Question 1860: Transition metals possess variable oxidation states because they have Options:
  A) Electrons in the d orbitals
  B) Electron in the s orbitals
  C) A variable number of electrons in the p orbitals
  D) Partially filled p orbitals
  Show Answer
  The correct answer is A .