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JAMB Chemistry 2015 Paper

Question : 63

Total: 64

Solution:

Concept:

Relative molecular mass is the sum of the atomic masses of all atoms in one molecule of the compound.

Explanation:

Limestone has the formula

\mathrm{CaCO}_3

It contains

1

calcium atom,

1

carbon atom, and

3

oxygen atoms.

So, relative molecular mass

= (1 \times \mathrm{Ar\ of\ Ca}) + (1 \times \mathrm{Ar\ of\ C}) + (3 \times \mathrm{Ar\ of\ O})

Substitute the given atomic masses:

= (1 \times 40) + (1 \times 12) + (3 \times 16)

Calculate:

40 + 12 + 48 = 100

Thus, the relative molecular mass of

\mathrm{CaCO}_3

100

Answer:

100

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