20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample ?
(At. Wt. : Mg = 24)
(1) 60 (2) 84
(3) 75 (4) 96
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Answer:
MgCO3→MgO+CO2
The molar masses of MgCO3 and MgO are 24+12+48=84 g/mol and 24+16=40 g/mol respectively.
Thus, 8 g MgO will be obtained from 4084×8=16.8 mg of MgCO3.
The percentage purity of magnesium carbonate in the sample is 2016.8×100=80%
your answer should be 80 and not 84
Hence, the correct option is B
Explanation:
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