A 500 g toothpaste sample has `0.2` g fluoride concentration. What is the concentration of `F^(Theta)` in ppm ?

Options

A. `250`
B. `200`
C. `400`
D. `1000`

Answer

To find the concentration of fluoride ions (F^-) in parts per million (ppm) from a 500 g toothpaste sample containing 0.2 g of fluoride, we can follow these steps:

### Step 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 grams) per million grams of the solution.

### Step 2: Set up the formula for ppm
The formula for calculating ppm is:
\[ \text{ppm} = \left( \frac{\text{mass of solute (g)}}{\text{mass of solution (g)}} \right) \times 10^6 \]

### Step 3: Identify the values from the question
From the question:
- Mass of fluoride (solute) = 0.2 g
- Mass of toothpaste (solution) = 500 g

### Step 4: Substitute the values into the ppm formula
Now, we can substitute the values into the ppm formula:
\[ \text{ppm} = \left( \frac{0.2 \, \text{g}}{500 \, \text{g}} \right) \times 10^6 \]

### Step 5: Calculate the concentration in ppm
Calculating the above expression:
\[ \text{ppm} = \left( \frac{0.2}{500} \right) \times 10^6 \]
\[ \text{ppm} = 0.0004 \times 10^6 \]
\[ \text{ppm} = 400 \]

### Conclusion
The concentration of fluoride ions (F^-) in the toothpaste sample is **400 ppm**.

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