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NEET 2015
Exam
NEET
Year
2015
Subject
Chemistry
Chapter
Some Basic Concepts of Chemistry

NEET 2015 · Chemistry · Some Basic Concepts of Chemistry

20.0 g of a magnesium carbonate sample decomposes on heating to...

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

MgCO3(s)⟶MgO(s)+CO2(g)MgC{O}_{3}\left(s\right) ⟶ MgO\left(s\right) + C{O}_{2}\left(g\right)

MolesofMgCO3=2084=0.238molMolesofMgC{O}_{3} = \dfrac{20}{84} = 0.238mol

From above equation.

1 mole MgCO3MgC{O}_{3} gives 1 mole MgO

∴∴ 0.238 mole MgCO3MgC{O}_{3} will give 0.238 mole MgO

=0.238×40g=9.523gMgO= 0.238 \times 40g = 9.523gMgO

PracticalyieldofMgO=8gMgOPracticalyieldofMgO = 8gMgO

∴∴ %Purity = \dfrac{8}{9.523} \times 100 = 84%
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