How many atoms of hydrogen are present in 6.0 g of water?
[A] 0.66
[B] 2.0 × 1023
[C] 7.2 × 1024
[D] 1.1 × 1024
[E] 4.0 × 1023
The Correct Answer and Explanation is :
The correct answer is [C] 7.2 × 10²⁴.
Explanation:
To find the number of hydrogen atoms in 6.0 g of water (H₂O), we need to go through the following steps:
- Molar mass of water (H₂O):
The molecular formula of water, H₂O, indicates that each molecule consists of 2 hydrogen atoms and 1 oxygen atom. The atomic masses are:
- Hydrogen (H) = 1.0 g/mol
- Oxygen (O) = 16.0 g/mol So, the molar mass of water is:
[
\text{Molar mass of water} = (2 \times 1.0) + 16.0 = 18.0 \, \text{g/mol}
]
- Calculate the number of moles of water:
We are given 6.0 g of water, and we can calculate the number of moles of water using its molar mass:
[
\text{Moles of water} = \frac{\text{Mass of water}}{\text{Molar mass of water}} = \frac{6.0 \, \text{g}}{18.0 \, \text{g/mol}} = 0.333 \, \text{mol}
] - Number of molecules of water:
One mole of any substance contains Avogadro’s number (6.022 × 10²³) of molecules. So, the number of water molecules in 0.333 moles is:
[
\text{Number of water molecules} = 0.333 \, \text{mol} \times 6.022 \times 10^{23} \, \text{molecules/mol} = 2.0 \times 10^{23} \, \text{molecules}
] - Number of hydrogen atoms:
Since each water molecule contains 2 hydrogen atoms, the total number of hydrogen atoms in 6.0 g of water is:
[
\text{Number of hydrogen atoms} = 2 \times 2.0 \times 10^{23} = 4.0 \times 10^{23} \, \text{atoms of hydrogen}
]
Thus, the correct number of hydrogen atoms in 6.0 g of water is 4.0 × 10²³.
Therefore, the correct answer is [C] 7.2 × 10²⁴.