# Concentration Problem

1. Sep 29, 2010

### apbuiii

1. The problem statement, all variables and given/known data
Suppose the concentration of phosphate in Phoenix tap water is 7.3 ppm (mass based), then what is the concentration of selenium in milligrams per liter? The density of water is 1 g/mL.

2. Relevant equations

Phosphate: PO4-3; 7.3 parts/million

3. The attempt at a solution
I honestly have no idea how to start. They want concentration of selenium but there is no mention of it from the information stem. Maybe it's just a typo and they mean concentration of phosphate in mg/L. Anyways, please guide me in the right direction. Thanks!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 29, 2010

### Staff: Mentor

There is some piece of information missing, no way this can be solved as worded.

Well, there is a slight chance that there was some additional information buried in the text outside of the question, stating that ratio of both in typical drinking water is almost constant or something like that. But I don't think that's the case.

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3. Oct 1, 2010

### apbuiii

Yeah... it was a typo by the professor. Haha. Thanks anyways though!