A 500 g toothpaste sample has 0.4 g fluoride concentration. The fluoride concentration in terms of ppm will be

Options

A. 200
B. 400
C. 500
D. 800

Answer

To find the fluoride concentration in terms of parts per million (ppm) from a 500 g toothpaste sample containing 0.4 g of fluoride, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of ppm**:
Parts per million (ppm) is a way of expressing very dilute concentrations of substances. It is defined as the mass of the solute (in this case, fluoride) divided by the mass of the solution (the toothpaste sample), multiplied by 1,000,000.

2. **Identify the Given Values**:
- Mass of fluoride = 0.4 g
- Mass of toothpaste sample = 500 g

3. **Set Up the ppm Formula**:
\[ \text{ppm} = \left( \frac{\text{mass of solute}}{\text{mass of solution}} \right) \times 10^6 \]

4. **Substitute the Values into the Formula**:
\[ \text{ppm} = \left( \frac{0.4 \, \text{g}}{500 \, \text{g}} \right) \times 10^6 \]

5. **Calculate the Fraction**:
\[ \frac{0.4}{500} = 0.0008 \]

6. **Multiply by 1,000,000**:
\[ \text{ppm} = 0.0008 \times 10^6 = 800 \]

7. **Final Result**:
The fluoride concentration in the toothpaste sample is **800 ppm**.