Help me solve this problem??

Question

You have prepared a solution by dissolving 232.29mg of copper(II) nitrate pentahydrate in 1.45kg of water. What is this solution's Cu+2 concentration in parts per million, ppm? (show steps)

Answer 1

Assuming ppm is parts per million by mass: 1ppm Cu²⁺ is the same as 10^-6 g Cu²⁺/g W (dilute assumed)

or, for this problem, find g Cu²⁺/ g Water and multiply by 10⁶ to get ppm

First you have to figure out the mg of Cu²⁺ ions:

mass of Cu(NO₃)₃ * molar mass of Cu/molar mass of Cu(NO₃)₂ = 232.29 mg *(63.55/187.56) = 78.706 mg Cu²⁺

You can take the ratio of masses and and covert it to g/g:

78.706 mg Cu²⁺/1.45 kg W * 1 g/1000mg * 1 kg/ g = 54.28 x 10^-6 g Cu²⁺/g W

Now multiply by 10⁶ and you get 54.28 ppm. Note that if you just took the ratio of mg of solute to kg of water, that is already in ppm because mg are 10^-6 kg - something you can use in the future.

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