Total number of atoms in 90 g of water are.........

Answer

To find the total number of atoms in 90 g of water (H₂O), we can follow these steps:

### Step 1: Determine the molecular formula of water
Water has the molecular formula H₂O, which means each molecule of water contains:
- 2 hydrogen (H) atoms
- 1 oxygen (O) atom

Thus, each molecule of water contains a total of:
\[ 2 \text{ H atoms} + 1 \text{ O atom} = 3 \text{ atoms} \]

### Step 2: Calculate the molar mass of water
The molar mass of water can be calculated as follows:
- Hydrogen (H) has an atomic mass of approximately 1 g/mol. Since there are 2 hydrogen atoms:
\[ 2 \times 1 = 2 \text{ g/mol} \]
- Oxygen (O) has an atomic mass of approximately 16 g/mol. Therefore:
\[ 1 \times 16 = 16 \text{ g/mol} \]
- Adding these together gives the molar mass of water:
\[ 2 \text{ g/mol} + 16 \text{ g/mol} = 18 \text{ g/mol} \]

### Step 3: Calculate the number of moles of water in 90 g
We can calculate the number of moles of water using the formula:
\[ \text{Moles of water} = \frac{\text{mass of water (g)}}{\text{molar mass of water (g/mol)}} \]
Substituting the values:
\[ \text{Moles of water} = \frac{90 \text{ g}}{18 \text{ g/mol}} = 5 \text{ moles} \]

### Step 4: Calculate the total number of atoms
Since we know that 1 mole of water contains 3 moles of atoms, we can calculate the total number of moles of atoms in 5 moles of water:
\[ \text{Total moles of atoms} = 5 \text{ moles of water} \times 3 \text{ moles of atoms/mole of water} = 15 \text{ moles of atoms} \]

### Step 5: Convert moles of atoms to number of atoms
To find the total number of atoms, we use Avogadro's number, which is approximately \( 6.02 \times 10^{23} \) atoms/mole:
\[ \text{Total number of atoms} = 15 \text{ moles of atoms} \times 6.02 \times 10^{23} \text{ atoms/mole} \]
Calculating this gives:
\[ \text{Total number of atoms} = 15 \times 6.02 \times 10^{23} \approx 9.03 \times 10^{24} \text{ atoms} \]

### Final Answer
The total number of atoms in 90 g of water is approximately \( 9.03 \times 10^{24} \) atoms.

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