Answer:
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
