The water (1250 kg) in an aquarium tank was with 5 mg of mercury. What is concentration of mercury in ppm.

Answer

To find the concentration of mercury in parts per million (ppm) in the aquarium tank, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of ppm**:
- ppm (parts per million) is defined as the mass of the solute (in this case, mercury) divided by the mass of the solution (water), multiplied by \(10^6\).

2. **Identify the Mass of Mercury**:
- The mass of mercury given is 5 mg.
- Convert this to grams:
\[ 5 \text{ mg} = 5 \times 10^{-3} \text{ grams} \]

3. **Identify the Mass of the Solution**:
- The mass of water in the aquarium is 1250 kg.
- Convert this to grams:
\[ 1250 \text{ kg} = 1250 \times 10^3 \text{ grams} = 1,250,000 \text{ grams} \]

4. **Substitute into the ppm Formula**:
- Now, substitute the values into the ppm formula:
\[ \text{ppm} = \left( \frac{\text{mass of mercury}}{\text{mass of solution}} \right) \times 10^6 \]
- Plugging in the values:
\[ \text{ppm} = \left( \frac{5 \times 10^{-3}}{1,250,000} \right) \times 10^6 \]

5. **Calculate the ppm**:
- First, simplify the fraction:
\[ \frac{5 \times 10^{-3}}{1,250,000} = \frac{5}{1,250,000} \times 10^{-3} \]
- Now, calculate:
\[ \text{ppm} = \frac{5}{1,250,000} \times 10^6 = \frac{5 \times 10^6}{1,250,000} \]
- This simplifies to:
\[ \text{ppm} = \frac{5 \times 10^6}{1.25 \times 10^6} = 0.004 \]

6. **Final Answer**:
- Therefore, the concentration of mercury in the aquarium water is:
\[ \text{Concentration of mercury} = 0.004 \text{ ppm} \]