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    I've looked around on how to do these but i just need clearer understanding.

    How would i answer this question for example?

    (iii) 1 kg of a solution contains 0.100 mol of calcium ions, Ca2+.
    What is the concentration of the calcium ions by mass in
    parts per million (ppm)?
    [Assume the relative atomic mass of calcium is 40.]
    (2)
    ................................ ................................ .......................ppm

    This is from Edexcel May 2010 Unit 1 paper.
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    ppm means: how many units of a solute do you have in 1,000,000 units of the solvent? Bear in mind you have to use the same unit for both.
    So I assume you know how to calculate the mass of Ca2+ that you have in the solution? (Answer will be in grams)
    You've got 1000g of solution, but since you need the mass of solute in 1,000,000 grams..multiply your answer from above by 1,000.
 
 
 
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