To find the mass of 1.22 moles of water (H₂O), we need to use the concept of molar mass. The molar mass of a substance is the mass in grams of one mole of that substance.
1. Identify the molar mass of water (H₂O):
- The molecular formula for water is H₂O, which means it has 2 hydrogen atoms and 1 oxygen atom.
- The atomic masses are approximately:
- Hydrogen (H): 1.008 grams per mole
- Oxygen (O): 16.00 grams per mole
- Therefore, the molar mass of water is:
[tex]\[
2 \times 1.008 \, \text{g/mol} + 16.00 \, \text{g/mol} = 18.016 \, \text{g/mol}
\][/tex]
2. Calculate the total mass of water:
- We have 1.22 moles of water.
- The total mass can be found by multiplying the number of moles by the molar mass:
[tex]\[
\text{Mass of water} = 1.22 \, \text{moles} \times 18.015 \, \text{g/mol}
\][/tex]
Performing the multiplication gives:
[tex]\[
\text{Mass of water} \approx 21.9783 \, \text{grams}
\][/tex]
3. Express the mass to three significant figures:
- To report the mass with three significant figures, we round 21.9783 grams to 21.978 grams.
Therefore, the mass of 1.22 moles of water, expressed to three significant figures, is 21.978 grams.
