Some Basic Concepts of Chemistry 1 Question 15
36. The weight of $1 \times 10^{22}$ molecules of $\mathrm{CuSO}{4} \cdot 5 \mathrm{H}{2} \mathrm{O}$ is (1991, 1M)
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Solution:
- Molar mass of $\mathrm{CuSO}{4} \cdot 5 \mathrm{H}{2} \mathrm{O}$
$$ \begin{aligned} & =63.5+32+4 \times 16+5 \times 18 \ & =249.5 \mathrm{~g} \end{aligned} $$
Also, molar mass represents mass of Avogadro number of molecules in gram unit, therefore
$\because 6.023 \times 10^{23}$ molecules of $\mathrm{CuSO}{4} \cdot 5 \mathrm{H}{2} \mathrm{O}$ weigh $249.5 \mathrm{~g}$
$\therefore 10^{22}$ molecules will weigh $\frac{249.5}{6.023 \times 10^{23}} \times 10^{22}=4.14 \mathrm{~g}$
