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Tuesday, 16 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 71:
A molar solution of caustic soda is prepared by dissolving
  • A 40 g NaOH in 100 g of water
  • B 40 g NaOH in 1000 g of water
  • C 20 g NaOH in 500 of solution
  • D 20 g NaOH in 1000 g of solution
  • E 2o g NaOH in 80 g of solution
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Question 72:
Which of the following mixtures would result in a solution of pH greater than 7?
  • A 25.00 cm<sup style='font-size: smaller;'>3</sup> of 0.05 M H<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub> and 25.00cm<sup style='font-size: smaller;'>3</sup> of 0.50 M Na<sub style='font-size: smaller;'>2</sub>CO<sub style='font-size: smaller;'>3</sub>
  • B 25.00 cm<sup style='font-size: smaller;'>3</sup> of 0.05 M H<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub> and 25.00 cm<sup style='font-size: smaller;'>3</sup> of 0.10 M NaHCO<sub style='font-size: smaller;'>3</sub>
  • C 25.00 cm<sup style='font-size: smaller;'>3</sup> of 0.11 MH<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub> and 25.00cm<sup style='font-size: smaller;'>3</sup> 0. 10 M NaOH
  • D 25.00cm<sup style='font-size: smaller;'>3</sup> of 0.11 MH<sub style='font-size: smaller;'>2</sub> SO<sub style='font-size: smaller;'>4</sub> and 50.00 cm<sup style='font-size: smaller;'>3</sup> of 0.05 M NaOH
  • E 25.00cm<sup style='font-size: smaller;'>3</sup> of 0.25 M H<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub> and 50.00cm<sup style='font-size: smaller;'>3</sup> of 0.20 M NaOH
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Question 73:
Sulphur
  • A Forms two alkaline oxides
  • B Is spontaneously flammable
  • C Burns with a blue flame
  • D Conducts electricity in the molten state
  • E Is usually stored in the form of sicks in water
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Question 74:
An organic compound with a vapour density 56.5 has the following percentage composition:C =53.1% N = 12.4%, O = 28.3%, H = 6.2%. The molecular formula of the compound is
Relative atomic masses: N = 14, O = 16, C = 12, H = 1 )
  • A C<sub style='font-size: smaller;'>3</sub>H<sub style='font-size: smaller;'>6</sub>O<sub style='font-size: smaller;'>2</sub>N
  • B C<sub style='font-size: smaller;'>5</sub>H<sub style='font-size: smaller;'>6</sub>O<sub style='font-size: smaller;'>2</sub>N
  • C (C<sub style='font-size: smaller;'>5</sub>H<sub style='font-size: smaller;'>7</sub>O<sub style='font-size: smaller;'>2</sub>N)<sub style='font-size: smaller;'>1/2</sub>
  • D C<sub style='font-size: smaller;'>5</sub>H<sub style='font-size: smaller;'>7</sub>O<sub style='font-size: smaller;'>2</sub>N
  • E (C<sub style='font-size: smaller;'>5</sub>H<sub style='font-size: smaller;'>7</sub>O<sub style='font-size: smaller;'>2</sub>N)<sub style='font-size: smaller;'>2</sub>
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Question 75:
Which of the following statements is INCORRECT?
  • A Fractional distillation of crude petroleum will give the folloing hydrocarbon fuels in order of increasing boiling point
  • B Butane < petrol < kerosene of polythene.
  • C Both but-1-ene and but-1-yne will decolorize bromine readily
  • D But-2-ene will react with chlorine to form 2,3-dichlorobutane
  • E Calcuim carbide will react with water to form any alkyne
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