Answer
(a)The weight of magnesium carbonate=73.425g
(b)The weight of impurities=201.575g
(c)The weight of magnesium=21.17g
Work Step by Step
(a)The weight of magnesium carbonate=Total mass of ore$\times$ Percent mass of magnesium carbonate=$275\times26.7\%=73.425g$
(b)The weight of impurities=Total mass of ore-mass of magnesium carbonate=$275-73.425=201.575g$
(c) Molar mass of Magnesium=24.305amu
The molar mass of magnesium carbonate=84.314amu
The percent composition of Magnesium in Magnesium carbonate:
Percent composition of magnesium=$\frac{\text{molar mass magnesium}}{\text{molar mass magnesium carbonate}}\times100=\frac{24.305}{84.314}\times100=28.83\%$
Weight of Magnesium in 73.425g magnesium carbonate(275g ore sample):
Weight of Magnesium=weight of magnesium carbonate$\times$percent composition of magnesium=$73.425\times28.83\%\approx21.17g$
