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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 106:
A mixture of starch solution and potassium iodide was placed in a test tube. On adding dilute tetraoxosulphate (lV) acid and then K2Cr2O7 solutions, a blue-black colour was produced. In this reaction, the?
  • A Iodide is oxidized
  • B Tetraoxosulphate (Vl) acid acts as an oxidizing agent
  • C Starch has been oxidized
  • D K<sub style='font-size: smaller;'>2</sub>Cr<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>7</sub> is oxidized
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Question 107:
Which of the followingstatements is TRUE?
  • A The dissolution of NaOH<sub style='font-size: smaller;'>(s)</sub> in water is endothermic
  • B The heat os solution of NaOH<sub style='font-size: smaller;'>(s)</sub> is positive
  • C The NaOH<sub style='font-size: smaller;'>(s)</sub> gains heat from the surroundings
  • D The heat of solution of NaOH<sub style='font-size: smaller;'>(s)</sub> is negative
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Question 108:
Aluminium is extracted commercially from its ore by?
  • A Heating aluminium oxide with coke in a furance
  • B The electrolysis of fused aluminium oxide in cryolite
  • C Treating cryolite with sodium hydroxide solution under prressure
  • D Heating sodium aluminium silicate to a high temperature
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Question 109:
The forces holding naphthalene crystals together can be overcome when naphthalene is heated to a temperature of 354K resulting in the crystal to melting. These forces are known as?
  • A Coulombic
  • B Ionic
  • C Covalent
  • D Van der waals
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Question 110:
The energy changes accompanying the addition of an electron to a gaseous atom is called?
  • A First ionization energy
  • B Second ionization energy
  • C Electron affinity
  • D Electronegativity
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