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Some Basic Concepts of Chemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistrySome Basic Concepts of Chemistry3 Marks
Question
How are $0.50 \mathrm{~mol} \mathrm{Na}_2 \mathrm{CO}_3$ and $0.50 \mathrm{M} \mathrm{Na}_2 \mathrm{CO}_3$ different?
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Answer

Molar mass of $\mathrm{Na}_2 \mathrm{CO}_3=(2 \times 23)+12.00+(3 \times 16)$
$=106 \mathrm{~g} \mathrm{~mol}^{-1}$
Now, 1 mole of $\mathrm{Na}_2 \mathrm{CO}_3$ means 106 g of $\mathrm{Na}_2 \mathrm{CO}_3$.
$\therefore 0.5 \mathrm{~mol}$ of $\mathrm{Na}_2 \mathrm{CO}_3=\frac{106 \mathrm{~g}}{1 \mathrm{~mole}} \times 0.5 \mathrm{~mol} \mathrm{Na}_2 \mathrm{CO}_3$
$=53 \mathrm{~g} \mathrm{Na}_2 \mathrm{CO}_3$
$\Rightarrow 0.50 \mathrm{M}$ of $\mathrm{Na}_2 \mathrm{CO}_3=0.50 \mathrm{~mol} / \mathrm{L} \mathrm{Na}_2 \mathrm{CO}_3$
Hence, 0.50 mol of $\mathrm{Na}_2 \mathrm{CO}_3$ is present in 1 L of water or 53 g of $\mathrm{Na}_2 \mathrm{CO}_3$ is present in 1 L of water.

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