What is the molar concentration of Cu2 + in a solution that is labelled 5 ppm Cu2+? a) 7.9x10^ (-5) M b) 7.9x10^ (-6) M c) 5.1x10^ (-6) M d) 5.5x10^ (-4) M

1.24x10⁻⁴ mol/L

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Explanation:

5 ppm is a sort of concentration that indicates:

weigh of solute x 10⁶ / weigh of solution or volume of solution.

Relation must be in the order of 10⁻⁶, for example mg/kg / μg/g.

We can also write ppm as μg/mL, so 5 ppm will be understood as 5 μg of Ca²⁺ in 1mL of solution.

This would be the rule of three to reach molarity

In 1mL we have 5 μg of Ca²⁺

In 1000 mL we would have 5000 μg of Ca²⁺

Let's convert 5000 μg to g (1g = 1x10⁶μg)

5000 μg = 5x10⁻³ g

Now, that we have the mass, we convert it to moles (mass / molar mass)

5x10⁻³ g / 40.08g/m = 1.24x10⁻⁴ moles

As this moles are in 1000mL (1L) it's molarity