Question

Calculate the number of formula units of $N{a}_{2}S{O}_4$ in $\frac{4}{9}$ millimoles of a pure sample of $N{a}_{2}S{O}_4$.

• A. $24.088\times {10}^{23}$
• B. $2.41\times {10}^{20}$
• C. $2.68\times {10}^{20}$
• D. $2.68\times {10}^{23}$

Answer 1

The correct option is C $2.68\times {10}^{20}$

We know,
1 mole of $N{a}_{2}S{O}_4=6.022\times {10}^{23}$ formula units of $N{a}_{2}S{O}_4$.

So, 1 millimole of $N{a}_{2}S{O}_4=6.022\times {10}^{20}$ formula units of $N{a}_{2}S{O}_4$.

Therefore, $\frac{4}{9}$ millimoles of $N{a}_{2}S{O}_4$
$=6.022\times {10}^{20}\times \frac{4}{9}$ formula units
$=2.68\times {10}^{20}$ formula units of $N{a}_{2}S{O}_4$