Answer :
To find out how many molecules of water are in 6.00 grams of water, we can follow these steps:
1. Find the molar mass of water.
2. Calculate the number of moles of water in 6.00 grams.
3. Use Avogadro's number to find the number of molecules.
**Step 1: Find the molar mass of water (H₂O).**
The molar mass of an element or compound is the mass in grams of 1 mole of that substance. For water, this involves the molar masses of hydrogen (H) and oxygen (O).
The molar mass of hydrogen is approximately 1.008 g/mol, and since water has two hydrogen atoms, we multiply this by 2.
For oxygen, the molar mass is approximately 16.00 g/mol.
Thus, the molar mass of water (H₂O) is:
\(2 \times 1.008 \text{ g/mol} + 16.00 \text{ g/mol} = 2.016 \text{ g/mol} + 16.00 \text{ g/mol} = 18.016 \text{ g/mol}\)
**Step 2: Calculate the number of moles of water in 6.00 grams.**
Using the molar mass of water, we can find out how many moles are in 6.00 grams of water with the following formula:
\[ \text{Number of moles} = \frac{\text{Mass of the substance}}{\text{Molar mass of the substance}} \]
\[ \text{Number of moles of water (n)} = \frac{6.00 \text{ g}}{18.016 \text{ g/mol}} \approx 0.333 \text{ moles of water} \]
**Step 3: Use Avogadro's number to find the number of molecules.**
Avogadro's number is \(6.022 \times 10^{23}\) molecules/mol, which is the number of molecules in one mole of any substance.
To find the total number of water molecules in 0.333 moles, multiply the number of moles by Avogadro's number:
\[ \text{Number of molecules of water} = 0.333 \text{ moles} \times 6.022 \times 10^{23} \text{ molecules/mol} \]
\[ \text{Number of molecules of water} ≈ 2.01 \times 10^{23} \text{ molecules} \]
Therefore, 6.00 grams of water contains approximately \(2.01 \times 10^{23}\) molecules of water.
