If I am calculating the molarity of a solution in which more than one solute is dissolved, can I add the total number of moles of all the solutes together and divide it by the total volume of solvent to get the molarity of my solution?

  • $\begingroup$ Generally molarity/concentration is calculated on a per-solute basis rather than on a combined basis so I don't think adding them together would make sense $\endgroup$
    – IT Tsoi
    Apr 17 '17 at 4:35

It doesn't make sense to add the total number of moles then divide by volume to find molarity. By doing that you are assuming that all the solutes have the same concentration which is not true(you are finding an average concentration of the solution but it's not necessarily correct). The solution contains different solutes at different concentrations. I think what you're doing only works if you know that the concentrations of solutes in the solution are the same.

  • $\begingroup$ actually, I have X grams of A and Y grams of B and I dissolved it in Z ml of my solvent C now I would like to know the concentration of my solution $\endgroup$
    – Chemist
    Apr 17 '17 at 6:09
  • 1
    $\begingroup$ Concentration in what? Usually, we say concentration in A and concentration in B, so those should be separate... $\endgroup$
    – Zhe
    Apr 19 '17 at 3:41

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