Questions: How many grams of water are needed to react with 36.2 grams of Li2O? Given: Li2O + H2O → 2 LiOH 2.12 38.94 21.8 1.21 none of the above

Solution Steps

The balanced chemical equation for the reaction is: \[ \mathrm{Li}_{2} \mathrm{O} + \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{LiOH} \]

Calculate the molar masses of the reactants:

• Molar mass of \(\mathrm{Li}_{2} \mathrm{O}\): \[ 2 \times \text{Li} + \text{O} = 2 \times 6.941 + 15.999 = 13.882 + 15.999 = 29.881 \, \text{g/mol} \]
• Molar mass of \(\mathrm{H}_{2} \mathrm{O}\): \[ 2 \times \text{H} + \text{O} = 2 \times 1.008 + 15.999 = 2.016 + 15.999 = 18.015 \, \text{g/mol} \]

Convert 36.2 grams of \(\mathrm{Li}_{2} \mathrm{O}\) to moles: \[ \text{moles of } \mathrm{Li}_{2} \mathrm{O} = \frac{36.2 \, \text{g}}{29.881 \, \text{g/mol}} = 1.211 \, \text{mol} \]

From the balanced equation, 1 mole of \(\mathrm{Li}_{2} \mathrm{O}\) reacts with 1 mole of \(\mathrm{H}_{2} \mathrm{O}\). Therefore, 1.211 moles of \(\mathrm{Li}_{2} \mathrm{O}\) will react with 1.211 moles of \(\mathrm{H}_{2} \mathrm{O}\).

Convert moles of \(\mathrm{H}_{2} \mathrm{O}\) to grams: \[ \text{grams of } \mathrm{H}_{2} \mathrm{O} = 1.211 \, \text{mol} \times 18.015 \, \text{g/mol} = 21.80 \, \text{g} \]

Final Answer