If 1000g of water from Luboc River contains 0.0075g of Ca2+ ion, what is the concentration in ppm by mass of Ca2+ present in Luboc River?

7.5 ppm

Given

1000 g of water

0.0075g of Ca²⁺ ion

Required

the concentration in ppm by mass of Ca²⁺

Solution

ppm = part per million

solvent = water ⇒ ppm = 1 mg/L(water density is 1 kg / L) or mg/kg

Convert g to mg of  Ca²⁺ ion :

0.0075 g = 7.5 x 10⁻³ g = 7.5 mg

Convert g to kg of water :

1000 g = 1 kg water

So the concentration of Ca²⁺ ion :

= 7.5 mg / 1 kg

= 7.5 ppm

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