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NEET2015ChemistrySome Basic Concepts of ChemistryActual

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight: Mg = 24)

Options

  1. A75
  2. B96
  3. C60
  4. D84

Correct answer

D. 84

Step-by-step solution

M g C O 3 s ⟶ M g O s + C O 2 g M o l e s   o f   M g C O 3 = 20 84 = 0.238   m o l From above equation. 1 mole M g C O 3 gives 1 mole MgO ∴ 0.238 mole M g C O 3 will give 0.238 mole MgO = 0.238 × 40   g = 9.523   g   M g O P r a c t i c a l   y i e l d   o f   M g O = 8   g   M g O ∴ %   P u r i t y = 8 9.523 × 100 = 84 %

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