Sodium fluoride \( (\mathrm{NaF}) \) is commercially available in \( 100.0-\mathrm{lb} \) bags. Calculate the mass in kg of fluoride in a \( 100.0-\mathrm{lb} \) bag of sodium fluoride. Express the mass in kilograms to three significant figures.

To calculate the mass of fluoride in a \( 100.0 \, \text{lb} \) bag of sodium fluoride (\( \text{NaF} \)), we first need to determine the molar mass of sodium fluoride and the mass fraction of fluoride in it. 1. **Calculate the molar mass of sodium fluoride (\( \text{NaF} \))**: - Molar mass of sodium (\( \text{Na} \)): approximately \( 22.99 \, \text{g/mol} \) - Molar mass of fluorine (\( \text{F} \)): approximately \( 19.00 \, \text{g/mol} \) \[ \text{Molar mass of NaF} = 22.99 \, \text{g/mol} + 19.00 \, \text{g/mol} = 41.99 \, \text{g/mol} \] 2. **Calculate the mass fraction of fluoride in sodium fluoride**: \[ \text{Mass fraction of F} = \frac{\text{mass of F}}{\text{mass of NaF}} = \frac{19.00 \, \text{g/mol}}{41.99 \, \text{g/mol}} \approx 0.452 \] 3. **Convert the mass of sodium fluoride from pounds to grams**: - We know that \( 1 \, \text{lb} \) is approximately \( 453.592 \, \text{g} \). \[ 100.0 \, \text{lb} = 100.0 \times 453.592 \, \text{g} \approx 45359.2 \, \text{g} \] 4. **Calculate the mass of fluoride in the \( 100.0 \, \text{lb} \) bag**: \[ \text{Mass of F} = \text{mass of NaF} \times \text{mass fraction of F} = 45359.2 \, \text{g} \times 0.452 \approx 20493.7 \, \text{g} \] 5. **Convert the mass of fluoride from grams to kilograms**: \[ \text{Mass of F in kg} = \frac{20493.7 \, \text{g}}{1000} \approx 20.4937 \, \text{kg} \] 6. **Express the mass in kilograms to three significant figures**: \[ \text{Mass of F} \approx 20.5 \, \text{kg} \] Thus, the mass of fluoride in a \( 100.0 \, \text{lb} \) bag of sodium fluoride is approximately **20.5 kg**.