Answer
$49.5\text{ kg}$
Work Step by Step
We determine the volume of the lake:
$\text{Volume}=10.0\times 10^6\text{ m}^2\times 15\text{ m}=1.5\times 10^8\text{ m}^3$
Convert to liters:
$1.5\times 10^8\text{ m}^3\times 10^3\text{ L/m}^3=1.5\times 10^{11}\text{ L}$
The total mercury is:
$0.33\mu\text{g/L}\times 1.5\times 10^{11}\text{ L}=4.95\times 10^{10}\mu\text{g}$
Convert to grams:
$4.95\times 10^{10}\mu\text{g}\div 10^6=4.95\times 10^4\text{ g}$
Convert to kilograms:
$4.95\times 10^4\text{ g}\div 1000=49.5\text{ kg}$
