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 641: 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 642: Pure solvents are obtained by Options:
  A) Distillation
  B) Condensation
  C) Extraction
  D) Evaporation
  Show Answer
  The correct answer is A .
• Question 643:

  What is the PH of 0.00 1 moldm${}^3$ solution of the sodium hydroxide

  Options:
  A) 14
  B) 13
  C) 12
  D) 11
  Show Answer
  The correct answer is D .
• Question 644: A pair of compounds that can be used to generate a gas which has physiological effect on human beings is Options:
  A) sodium trioxonitrate (V) and calcium chloride
  B) sodium dioxonitrate (III) and ammonium chloride
  C) sodium trioxonitrate (V) and ammonium chloride
  D) sodium dioxonitrate (III) and potassium chloride
  Show Answer
  The correct answer is A .
• Question 645:

  What happens to the value of the equilibrium constant (Kc) for a reaction if the reaction is reversed?

  Options:
  A) It becomes zero
  B) It becomes negative
  C) It remains the same
  D) It becomes the reciprocal of the original value
  Show Answer
  The correct answer is D .
• Question 646:

  

  The IUPAC nomenclature for the compound above is

  Options:
  A) dimethlhexane
  B) 3,5 dimethylhexane
  C) 1.1 dmethyl, 3 methylpentane
  D) 2.4 dimethylhexane
  Show Answer
  The correct answer is D .
• Question 647: The alkanol obtained from the production of soap is Options:
  A) propanol
  B) ethanol
  C) glycerol
  D) methanol
  Show Answer
  The correct answer is C .
• Question 648:

  

  How many more isomers of the compound above can be obtained ?

  Options:
  A) 5
  B) 4
  C) 3
  D) 2
  Show Answer
  The correct answer is B .
• Question 649: CaO_s + H₂O_(l) → Ca(OH)_2(s) ΔH -65 kj. The process represented by the above equation is known as? Options:
  A) dissolution
  B) slaking
  C) liming
  D) mortaring
  Show Answer
  The correct answer is B .
• Question 650: How many cations will be produced from a solution of potassium aluminium tetraoxosulphate (VI)? Options:
  A) 3
  B) 4
  C) 1
  D) 2
  Show Answer
  The correct answer is D .