Question

What is the number of moles in 18 g of water (\( \text{H}_2\text{O} \))?

• A. 1 mol
• B. 0.5 mol
• C. 2 mol
• D. 0.25 mol

Hint:

Remember: The number of moles is calculated by dividing the mass of the substance by its molar mass.

Answer 1

The Correct Option is A

Step 1: Find the molar mass of water The molar mass of water (\( \text{H}_2\text{O} \)) is the sum of the atomic masses of hydrogen and oxygen: - Hydrogen (H) = 1 g/mol, - Oxygen (O) = 16 g/mol. The molar mass of \( \text{H}_2\text{O} \) is: \[ M_{\text{H}_2\text{O}} = (2 \times 1) + 16 = 18 \, \text{g/mol} \] Step 2: Use the formula to calculate the number of moles The number of moles (\( n \)) is given by: \[ n = \frac{\text{Mass}}{\text{Molar mass}} \] Substitute the given values: \[ n = \frac{18 \, \text{g}}{18 \, \text{g/mol}} = 1 \, \text{mol} \] Answer: Therefore, the number of moles in 18 g of water is 1 mol. So, the correct answer is option (1).