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JAMB Chemistry 2018 Paper

Question : 72

Total: 87

Solution:

Concept:

The percentage composition of an element in a compound is the mass of that element divided by the total molar mass of the compound, multiplied by

100\%

Explanation:

Calcium trioxocarbonate(IV) has the formula

\mathrm{CaCO}_3

Molar mass of oxygen atoms in the compound:

3 \times 16 = 48

Molar mass of

\mathrm{CaCO}_3 = 40 + 12 + 48 = 100

Percentage of oxygen

= \frac{48}{100} \times 100\%

Percentage of oxygen

= 48\%

Answer:

48\%

— Option B.

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