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2014-07-05T11:02:16-03:00
1000kg = 1.000.000g = 10^6g

0,2mg = 0,2 *10^-3g =  2*10^-1 * 10^-3 = 2*10^-4g

10^6 ---------------- 2*10^-4
1 -------------------------x

10^6x=2*10^-4
x = 2*10^-4/10^6
x = 2*10^-4*10^-6
x = 2*10^-10g de ouro para 1g de agua.

197g ---------------- 1 mol
2*10^-10 ------------- x mols

197x=2*10^-10
x = 2*10^-10/197
x = 200*10^-12 /197
x = 1,01*10^-12 ~= 10^-12 mols de ouro

1 mol ------------------ 6,02*10^23
10^-12 ----------------- x

x = 6,02*10^23*10^-12
x = 6,02*10^11 moléculas de ouro em 1 grama de água.
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