The question I'm trying to answer is below and the answer is C. enter image description here

I tried finding the total moles of copper(II) ions first by using mole ratios for copper(II) sulfate and copper(II) chloride, obtaining an answer of 0.42 moles. Then, I used $n=cv$ and obtained the concentration, using the volume in the question in litres, of 0.84, which is incorrect. Now, I'm sure my method incorrect but I can't think of another way to this.

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    $\begingroup$ Where are you getting your numbers from? They told you that 0.5 mol of $\ce{CuCl_2}$ and 0.5 mol of $\ce{CuSO_4}$ were placed together. That means you have 0.5 mol + 0.5 mol = 1 mol of copper ions. Divide that by the volume, which is given to you as 0.500 L, giving you 2.0 mol/L. Your numbers don’t seem to match up with the question at all. $\endgroup$ Commented Apr 3, 2016 at 13:54
  • $\begingroup$ @lightweaver Yes but the number of moles in the question are the moles of the two solutions, not the copper ions, I believe. $\endgroup$
    – user307397
    Commented Apr 3, 2016 at 14:09
  • $\begingroup$ @lightweaver I gor my number by using the ratio 1mol copper(ii):2mol chlorine and 1mol copper(ii):1 mol $So_4$ $\endgroup$
    – user307397
    Commented Apr 3, 2016 at 14:13
  • $\begingroup$ The question is: "What is the concentration of $\ce{Cu^{2+}_{(aq)}}$ ions in the solution in $mol\,l^{-1}$. $\endgroup$
    – aventurin
    Commented Apr 3, 2016 at 14:21
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    $\begingroup$ 1 mole copper(II) sulfate contains 1 mole $Cu^{2+}$, and 1 mole copper(II) chloride also contains 1 mole $Cu^{2+}$. $\endgroup$
    – aventurin
    Commented Apr 3, 2016 at 15:40

1 Answer 1


1 mole of copper(II) sulphate contains 1 mole of copper ($\ce{Cu^{2+}}$) and one mole of sulphate ($\ce{SO_4^{2-}}$). Or, if you want, 1 mole of copper, 1 mole sulphur, and 4 moles of oxygen.

This is by the definition of the mole as the unit of measurement for the amount of substance.

From this it follows that 0.5 moles of copper(II) sulphate contain 0.5 moles of copper. Similarly 0.5 moles of copper(II) chloride also contain 0.5 moles of copper. Together these are 1 mole of copper.

1 mole of copper ($\ce{Cu^{2+}}$) in $\mathrm{0.5\,l}$ water gives us a concentration of $\mathrm{2\, mol\,l^{-1}}$

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    $\begingroup$ Thank you sooooooo much!!!!!! n This made me everyhting completely clear! Couldn't thank you more. $\endgroup$
    – user307397
    Commented Apr 3, 2016 at 16:34

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