Posted by swtnblk on .
pleast help me work this prob
lead is a toxic meatal that affects the central nervous system. a Pbcontaminated water sample contains 0.0011% Pb by mass. What vilume of the water in milliliters contains 115g of Pb? (assume that the density of the solution is 1.0g/ml

chemistry 
MathMate,
0.0011% by mass means that for every 100 grams of solution (water), there is 0.0011 grams of lead.
By proportions noting 1 ml of water weighs 1 g:
100 ml : 0.0011 g
x ml : 115 g
So by cross multiplication:
x = 100*115/0.0011=10454545 ml
= 10454.545 l 
chemistry 
DrBob222,
I obtained the same number; I would express it as 1.0E4L to two significant figures.

chemistry 
MathMate,
Thanks Dr. Bob, I forgot about that!