1. **State the problem:** Find how many grams are in $8.20 \times 10^{22}$ molecules of $\mathrm{Li_2O}$. 2. **Formula and conversion factors:** To convert molecules to grams, use the following steps: - Convert molecules to moles using Avogadro's number: $$1\ \text{mol} = 6.02 \times 10^{23}\ \text{molecules}$$ - Convert moles to grams using molar mass: $$1\ \text{mol}\ \mathrm{Li_2O} = 29.881\ \text{g}$$ 3. **Set up the conversion:** $$8.20 \times 10^{22}\ \text{molecules}\ \mathrm{Li_2O} \times \frac{1\ \text{mol}\ \mathrm{Li_2O}}{6.02 \times 10^{23}\ \text{molecules}} \times \frac{29.881\ \text{g}\ \mathrm{Li_2O}}{1\ \text{mol}\ \mathrm{Li_2O}}$$ 4. **Calculate moles:** $$8.20 \times 10^{22} \times \frac{1}{6.02 \times 10^{23}} = \frac{8.20}{6.02} \times 10^{22-23} = 1.362 \times 10^{-1} \ \text{mol}$$ 5. **Calculate grams:** $$1.362 \times 10^{-1} \times 29.881 = 4.07 \ \text{g}$$ 6. **Final answer:** There are **4.07 grams** in $8.20 \times 10^{22}$ molecules of $\mathrm{Li_2O}$.