Some Basic Concepts of Chemistry - Result Question 41
####41. $20.0 g$ 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?
(a) 75
(b) 96
(c) 60
(d) 84
[2015 RS]
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Solution:
- (d) $MgCO_3 \longrightarrow MgO+CO_2$
$84 g$ of $MgCO_3$ form $40 g$ of $MgO$
$\therefore 20 g$ of $MgCO_3$ form $\frac{40 \times 20}{84} g$ of $MgO$
$=9.52 g$ of $MgO$
Since $8.0 g$ of $MgO$ is formed
Purity of sample $=\frac{8}{9.52} \times 100=84.0 %$
