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 141:

  MnO_2(s) + xHCl_(aq) → MnCl_2(aq) + yH₂O_(l) + zCl_2(g)

  In theequation above, what are the values of x, y and z respectively

  Options:
  A) 2, 1, 2
  B) 4, 1, 2
  C) 4, 2, 1
  D) 1, 2, 1
  Show Answer
  The correct answer is C .
• Question 142: Hydrogen can be displaced from a hot alkaline solution by Options:
  A) Fe
  B) Cu
  C) Ca
  D) Sn
  Show Answer
  The correct answer is A .
• Question 143: The bond which joins two ethanoic acid molecules in the liquid state is Options:
  A) a covalent bond
  B) an ionic bond
  C) a dative covalent bond
  D) a hydrogen bond
  Show Answer
  The correct answer is D .
• Question 144:

  Burning magnesium ribbon in air removes which of the following

  (i) oxygen (ii) nitrogen (iii) argon and (iv) carbon(iv)oxide?

  Options:
  A) i and iv only
  B) i, ii, iii and iv only
  C) i only
  D) i and ii only
  Show Answer
  The correct answer is C .
• Question 145: In the extraction of aluminum from purified bauxite by electrolysis, cryolite is used because Options:
  A) it makes bauxite a better conductor of electricity
  B) it makes bauxite melt at a lower temperature
  C) it makes aluminium purer
  D) it prevents aluminium from getting oxidized
  E) it protects the carbon electrodes used in the process
  Show Answer
  The correct answer is B .
• Question 146: As the difference in electronegativity between bonded atoms increases, polarity of the bond? Options:
  A) decreases
  B) increases
  C) remains unchanged
  D) reduces to zero
  Show Answer
  The correct answer is B .
• Question 147:

  A chemical reaction in which the hydration energy is greater than the lattice energy is referred to as

  Options:
  A) A reversible reaction
  B) A spontenous reaction
  C) An endothermic reaction
  D) An exothermic reaction
  Show Answer
  The correct answer is D .
• Question 148: In the purification of town water supply, alum is used principally to? Options:
  A) kill bacteria
  B) control the pH of water
  C) improve the taste of the water
  D) coagulate small pasrticles of mud
  Show Answer
  The correct answer is D .
• Question 149: Sucrose is made up of Options:
  A) glucose and glucose
  B) glucose and fructose
  C) fructose and fructose
  D) galactose and glucose
  Show Answer
  The correct answer is B .
• Question 150:

  The following are isoelectronic ions except

  Options:
  A) Na${}^{+}$
  B) Mg${}^{2+}$
  C) Si${}^{2+}$
  D) O${}^{2+}$
  Show Answer
  The correct answer is C .