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Post-UTME Chemistry 2018 Objective — Question 14

Question 14 of 21 from the Post-UTME Screening (Post-UTME) Chemistry 2018 Objective paper, with the correct answer and a full explanation.

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When carbon (IV) oxide is bubbled into lime water, a white precipitate is first formed, which later dissolves in excess CO2 to form a colourless solution. The white precipitate and the soluble compound formed in the reactions are respectively

  • A. Na2CO3 and NaHCO3
  • B. Na2CO3 and CaCl2
  • C. Ca(OH)2 and CaCO3
  • D. CaCO3 and Ca(HCO3)2Correct

Explanation

CO2 first forms insoluble CaCO3 with limewater; with excess CO2, this converts to soluble calcium hydrogencarbonate, Ca(HCO3)2.

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