All of the water in a `0.20M` solution of `NaCl` was evaporated and a `0.150` mol of `NaCl` was obtained. What the original volume of the sample?

Options

A. `30mL`
B. `333mL`
C. `750mL`
D. `1000mL`

Answer

To find the original volume of the `0.20 M` NaCl solution from which `0.150 moles` of NaCl was obtained after evaporation, we can use the formula for molarity:

### Step-by-Step Solution:

1. **Understand the Molarity Formula**:
Molarity (M) is defined as the number of moles of solute divided by the volume of solution in liters.
\[ M = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

2. **Identify the Given Values**:
- Molarity (M) = `0.20 M`
- Number of moles of NaCl = `0.150 moles`

3. **Rearrange the Molarity Formula**:
To find the volume of the solution, we can rearrange the formula:
\[ \text{Volume of solution in liters} = \frac{\text{Number of moles of solute}}{M} \]

4. **Substitute the Known Values**:
Now, substitute the values into the rearranged formula:
\[ \text{Volume} = \frac{0.150 \text{ moles}}{0.20 \text{ M}} \]

5. **Calculate the Volume**:
\[ \text{Volume} = \frac{0.150}{0.20} = 0.75 \text{ liters} \]

6. **Convert the Volume to Milliliters**:
Since the question may require the answer in milliliters, convert liters to milliliters:
\[ 0.75 \text{ liters} \times 1000 \text{ ml/liter} = 750 \text{ ml} \]

### Final Answer:
The original volume of the sample is **750 ml**.