What is the concentration in ppm of 2.000 g Pb for every 5.00 x 105 g of water?

Answer 1

5x10⁵ g is half a million g ( 0.5x10⁶ g)

2.000 g in half a million g is the same as 4 g in a million g

This is the same as 4 parts per million = 4.00 ppm