Question

Find the mass of oxygen in a sample of $H_2SO_4$ when $3.011 \times 10^{24}$ $H_2SO_4$ molecules are removed from 980 g of $H_2SO_4$.

$m_{H_2SO_4} = \frac{980}{98} = 10$ mol

Answer 1

320 g

Answer 2

1. Calculate initial moles of $H_2SO_4$: $\frac{980 \text{ g}}{98 \text{ g/mol}} = 10$ mol.
2. Calculate moles of $H_2SO_4$ removed: $\frac{3.011 \times 10^{24}}{6.022 \times 10^{23}} = 5$ mol.
3. Calculate moles of $H_2SO_4$ remaining: $10 \text{ mol} - 5 \text{ mol} = 5$ mol.
4. Calculate mass of $H_2SO_4$ remaining: $5 \text{ mol} \times 98 \text{ g/mol} = 490$ g.
5. Calculate mass fraction of oxygen in $H_2SO_4$: $\frac{4 \times 16}{98} = \frac{64}{98}$.
6. Calculate mass of oxygen in remaining sample: $490 \text{ g} \times \frac{64}{98} = 320$ g.