If 14.5 grams of mercury was found in 200 L of lake Ontario water, then what is the concentration of mercury in parts per million? Question 3 options: 14.5 0.00145 72.5 7.25 725 0.0000725

To find the concentration of mercury in parts per million (ppm), we need to follow these steps:

1. Convert the volume of water to grams:

   • The density of water is approximately 1 gram per milliliter (g/mL).
   • Since 1 liter (L) is 1000 milliliters (mL), 200 L of water is 200,000 mL.
   • Therefore, 200,000 mL of water is approximately 200,000 grams of water.

2. Calculate the concentration in ppm:

   • The formula for ppm is: $\text{ppm} = \left( \frac{\text{mass of solute (grams)}}{\text{mass of solution (grams)}} \right) \times 10^6$
   • Here, the mass of the solute (mercury) is 14.5 grams, and the mass of the solution (water) is 200,000 grams.
   • Plugging in the values: $\text{ppm} = \left( \frac{14.5}{200,000} \right) \times 10^6$

3. Perform the calculation:

   • First, divide 14.5 by 200,000: $\frac{14.5}{200,000} = 0.0000725$
   • Then, multiply by $10^6$: $0.0000725 \times 10^6 = 72.5$

Therefore, the concentration of mercury in parts per million is 72.5. The correct option is:

72.5