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Conclusion: There are approximately 0.556 moles, or 3.35 × 10²³ molecules, in 10 grams of water. The reasoning follows below.

Step 1: Calculate the Number of Moles

The molar mass of water (H₂O) is about 18.015 g/mol. This value is obtained from the atomic masses of hydrogen (approximately 1.008 g/mol) and oxygen (approximately 16.00 g/mol):

• 2 hydrogen atoms: 2 × 1.008, g/mol = 2.016, g/mol

• 1 oxygen atom: 16.00, g/mol

Thus, the molar mass of water is:

2.016 g/mol + 16.00 g/mol = 18.016 g/mol

However, for simplicity, we often use 18.015 g/mol.

Using the formula to find the number of moles:

$$\text{Number of moles} = \frac{\text{Mass of the substance}}{\text{Molar mass}}$$

we calculate:

$$\text{Number of moles} = \frac{10 , \text{g}}{18.015 , \text{g/mol}} \approx 0.556 , \text{moles}$$

Step 2: Calculate the Number of Molecules

To determine the number of molecules, we use Avogadro’s number, which is approximately 6.022 × 10²³ molecules per mole.

Number of molecules = Number of moles × 6.022 × 10²³ molecules/mol

This gives us:

Number of molecules = 0.556, moles × 6.022 × 10²³, molecules/mol ≈ 3.35 × 10²³ molecules

Therefore, 10 grams of water contains approximately 0.556 moles and 3.35 × 10²³ molecules.