"Suvarnabhasm", an ayurvedic drug, is found to contain `400 "ppm"` of colloidal gold. Mass `%` of gold `("atomic mass of Au" = 197)` will be :

Options

A. `0.040 %`
B. `7.88 %`
C. `0.0788 %`
D. `4xx10^(-4) %`

Explanation

To find the mass percentage of gold in "Suvarnabhasm", which contains 400 ppm of colloidal gold, we can follow these steps:

### Step 1: Understand the definition of ppm
PPM (parts per million) is defined as the mass of solute (in this case, gold) per mass of solution, multiplied by \(10^6\).

### Step 2: Set up the relationship
Given that there are 400 ppm of colloidal gold, this means:
\[ \text{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6 \]
Thus, for 400 ppm:
\[ 400 = \frac{\text{mass of gold}}{\text{mass of drug}} \times 10^6 \]

### Step 3: Assume a mass of the drug
To simplify calculations, we can assume the mass of the drug (solution) is \(10^6\) grams. Therefore, the mass of gold in this amount of drug can be calculated as follows:
\[ \text{mass of gold} = 400 \text{ grams} \]

### Step 4: Calculate mass percentage
Mass percentage is calculated using the formula:
\[ \text{Mass \%} = \left( \frac{\text{mass of solute}}{\text{mass of solution}} \right) \times 100 \]
Substituting the values:
\[ \text{Mass \% of gold} = \left( \frac{400 \text{ grams}}{10^6 \text{ grams}} \right) \times 100 \]

### Step 5: Simplify the calculation
\[ \text{Mass \% of gold} = \left( \frac{400}{10^6} \right) \times 100 = \frac{400 \times 100}{10^6} = \frac{40000}{10^6} = 0.04\% \]

### Conclusion
The mass percentage of gold in "Suvarnabhasm" is \(0.040\%\).