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Monday, 15 June 2026
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Chemistry Past Questions and Answers

Topic: Separation of mixtures and purification of chemical substances

Jamb Chemistry Questions - Separation of mixtures and purification of chemical substances

Question 61:
An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystaline solid, readily soluble in water. X contains the elements C, H and O in the atomic ratio 1: 2:1. The compound has a sweet teste and melts on heating. In the presence of yeast and in the absence of air, X is converted to compound Y and a colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a 'pop' sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet smelling compound W.
The molecular formula of X is
  • A C<sub style='font-size: smaller;'>12</sub>H<sub style='font-size: smaller;'>22</sub>O<sub style='font-size: smaller;'>11</sub>
  • B C<sub style='font-size: smaller;'>6</sub>H<sub style='font-size: smaller;'>12</sub>O<sub style='font-size: smaller;'>6</sub>
  • C C<sub style='font-size: smaller;'>3</sub>H<sub style='font-size: smaller;'>6</sub>O <sub style='font-size: smaller;'>3</sub>
  • D C<sub style='font-size: smaller;'>7</sub>H<sub style='font-size: smaller;'>14</sub>O<sub style='font-size: smaller;'>7</sub>
  • E C<sub style='font-size: smaller;'>12</sub>H<sub style='font-size: smaller;'>6</sub>O<sub style='font-size: smaller;'>4</sub>
View Answer & Explanation
Question 62:
An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystaline solid, readily soluble in water. X contains the elements C, H and O in the atomic ratio 1: 2:1. The compound has a sweet teste and melts on heating. In the presence of yeast and in the absence of air, X is converted to compound Y and a colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a 'pop' sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet smelling compound W.
Reaction of X with yeast forms the basis of the
  • A Plastic industry
  • B Textile industry
  • C Brewing industry
  • D Soap industry
  • E Dyeing industry
View Answer & Explanation
Question 63:
A mixture of common salt, ammonium chloride and barium sulphate can best be separated by
  • A Addition of water followed by filtration then sublimation
  • B Addition of water followed by sublimation then filtration
  • C Sublimation followed by addition of water then filtration
  • D Fractional distillation
  • E Fractional crystallization
View Answer & Explanation
Question 64:
How many isomeric forms are there for the molecular formula C3H6Br2?
  • A 1
  • B 2
  • C 3
  • D 4
  • E 5
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Question 65:
Crude petroleum pollutant usually seen on some Nigerian creeks and waterways can be dispersed or removed by
  • A Heating the affected parts in order to boil off the petroleum
  • B Mechanically stirring to dissolve the petroleum in water
  • C Pouring organic solvents to dissolve the petroleum
  • D Spraying the water with stergents
  • E Cooling to freeze out the petroleum
View Answer & Explanation