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KCET2010ChemistrySome Basic Concepts of Chemistry

A mixture of CaCl ₂ and NaCl weighing 4.44 ~g is treated with sodium carbonate solution to precipitate all the Ca ²⁺ ions as calcium carbonate. The calcium carbonate so obtained is heated strongly to get 0.56 ~g of CaO . The percentage of NaCl in the mixture (atomic mass of Ca =40 ) is

Options

  1. A75
  2. B30.6
  3. C25
  4. D69.4

Correct answer

A. 75

Step-by-step solution

1 ~mol CaCO ₃ 1 ~mol CaO + CO ₂ CaCl ₂+ Na ₂ CO ₃ 1 ~mol CaCO ₃ +2 Na 1 ~mol CaO 1 ~mol CaCl ₂ 0.56 56 ~mol CaO 0.01 ~mol CaCl ₂=0.01 111 ~g CaCl ₂=1.11 ~g CaCl ₂ Thus, in the mixture, weight of NaCl =4.44-1.11=3.33 ~g Percentage of NaCl = 3.33 4.44 100=75 %

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