The molar mass of `H_(2)O` is 18 g moll. What is the number of moles in 90 g water?

Options

A. 5
B. 11
C. `0.2`
D. 72

Answer

To find the number of moles in 90 g of water (H₂O), we can use the relationship between mass, molar mass, and the number of moles. Here’s how to solve the problem step by step:

### Step 1: Identify the molar mass of water
The molar mass of water (H₂O) is given as 18 g/mol.

### Step 2: Use the formula for calculating moles
The formula to calculate the number of moles (n) is:
\[ n = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]

### Step 3: Substitute the values into the formula
We have the mass of water as 90 g and the molar mass as 18 g/mol. Substituting these values into the formula gives:
\[ n = \frac{90 \text{ g}}{18 \text{ g/mol}} \]

### Step 4: Perform the calculation
Now, calculate the number of moles:
\[ n = \frac{90}{18} = 5 \]

### Step 5: Conclusion
Thus, the number of moles in 90 g of water is 5 moles.

### Final Answer
The number of moles in 90 g of water is **5 moles**.

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