Molarity of pure water is

Options

A. `18 M`
B. `10 M`
C. `55.5 M`
D. `1000 M`

Explanation

To find the molarity of pure water, we can follow these steps:

### Step 1: Understand the Definition of Molarity
Molarity (M) is defined as the number of moles of solute per liter of solution. In this case, we are considering pure water as the solution itself.

### Step 2: Determine the Volume of Water
We are given that we are considering 1 liter of pure water.

### Step 3: Find the Density of Pure Water
The density of pure water is approximately 1 gram per milliliter (g/mL). Since 1 liter is equal to 1000 mL, the mass of 1 liter of water can be calculated as follows:
\[ \text{Mass of water} = \text{Volume} \times \text{Density} = 1000 \, \text{mL} \times 1 \, \text{g/mL} = 1000 \, \text{grams} \]

### Step 4: Calculate the Moles of Water
To find the number of moles of water, we use the formula:
\[ \text{Moles of water} = \frac{\text{Mass of water}}{\text{Molar mass of water}} \]
The molar mass of water (H₂O) is approximately 18 g/mol. Therefore:
\[ \text{Moles of water} = \frac{1000 \, \text{grams}}{18 \, \text{g/mol}} \approx 55.56 \, \text{moles} \]

### Step 5: Calculate the Molarity of Pure Water
Now that we have the number of moles of water and the volume of the solution, we can calculate the molarity:
\[ \text{Molarity} = \frac{\text{Moles of solute}}{\text{Volume of solution in liters}} \]
Substituting the values we have:
\[ \text{Molarity} = \frac{55.56 \, \text{moles}}{1 \, \text{liter}} = 55.56 \, \text{M} \]

### Final Answer
The molarity of pure water is approximately **55.56 M**.

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