Question

How many moles are there in 10.8 g of water? (Hint: You need the Mr of water)
0.7
0.4
0.6
0.5

Answer 1

To calculate the number of moles of water in 10.8 grams, you first need to determine the molar mass (Mr) of water (H₂O).

The molar mass of water is calculated as follows:
- Hydrogen (H) has an atomic mass of approximately 1 g/mol, and there are 2 hydrogen atoms in water: \(2 \times 1 = 2 \, \text{g/mol}\)
- Oxygen (O) has an atomic mass of approximately 16 g/mol.
- Therefore, the molar mass of water is \(2 + 16 = 18 \, \text{g/mol}\).

Next, use the formula to calculate the number of moles:

\[
\text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}
\]

Substituting the values:

\[
\text{Number of moles} = \frac{10.8 \, \text{g}}{18 \, \text{g/mol}} = 0.6 \, \text{moles}
\]

So there are **0.6 moles** of water in 10.8 grams. The correct answer from the options provided is **0.6**.