Converting ppm to mg/L

[Cypher49]

1. The problem statement, all variables and given/known data
A is a stable powder
B is water
C is the product of the powder being in contact with water.

A is soluble in substance B and for every gram of A 10% is C.

For a concentration of 0.5ppm of C in twenty liters of water how many grams of A do you need?


3. The attempt at a solution
I went on the assumption that ppm=mg/l.
So 0.5ppm=0.5mg/l, and I would need 10mg for the twenty liters
Which means that I would need 100mg of A.

Is this correct?
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution

[Borek]

I would need 100mg of A.

Is this correct?

That would be my answer as well, although I find the wording of the question confusing.

[Cypher49]

Thanks for the confirmation, I'm just replying to say that 100mg was indeed the correct answer.

If you don't mind me asking, how did the wording confuse you?

[Borek]

If 0.1g of A reacted with water, what is mass of the product? Again 0.1g? Not impossible, but counterintuitive, at least to me.