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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 56:
The solubility curve of a solid X (molecular mass = 160) is as show above. 1,000 cm3 of a saturated solution of X at 80°C is cooled to 40°C . The weight of X crystalized out would be
  • A 10 g
  • B 12 g
  • C 14 g
  • D 16 g
  • E 18 g
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Question 57:
X is a crystalline salt of sodium solution of X in water turns litmus red and produces a gas which turns lime water milky when added to sodium carbonate. With barium chloride solution, X gives hydrochloric acid. X is
  • A Na <sub style='font-size: smaller;'>2</sub>CO <sub style='font-size: smaller;'>3</sub>
  • B NaHCO <sub style='font-size: smaller;'>3</sub>
  • C NaHSO <sub style='font-size: smaller;'>4</sub>
  • D Na <sub style='font-size: smaller;'>2</sub>SO <sub style='font-size: smaller;'>4</sub>
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Question 58:
X is a crystalline salt of sodium solution of X in water turns litmus red and produces a gas which turns lime water milky when added to sodium carbonate. With barium chloride solution, X gives hydrochloric acid. X is
  • A Na <sub style='font-size: smaller;'>2</sub>CO <sub style='font-size: smaller;'>3</sub>
  • B NaHCO <sub style='font-size: smaller;'>3</sub>
  • C NaHSO <sub style='font-size: smaller;'>4</sub>
  • D Na <sub style='font-size: smaller;'>2</sub>SO <sub style='font-size: smaller;'>4</sub>
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Question 59:
Some copper (ll) sulphate pentahydrate (CuSO4 5H2O), was heated at 120 oC with the following results. Wt of crucible = 10.00 g; Wt of crucible + CuSO4 5H2O =14.98g; Wt of crucible + residue = 13.54 g. How many molecules of water of crystalization were lost?
[H = 1, Cu = 63.5, O = 16, S = 32]
  • A 1
  • B 2
  • C 3
  • D 4
  • E 5
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Question 60:
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.
Compound W is
  • A A soap
  • B An oil
  • C An alkane
  • D An ester
  • E Sucrose
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