I think what you want to do is this.
Let's take a volume (choose anything but I'll pick 100 mL of the 0.2M NaCl) and calculate the amount of CaCl2 needed to meet the problem.
100 mL of 0.2M NaCl + xmL of 0.1M CaCl2, we have
millimols + charge = 100*0.2 = 20 for Na in NaCl and 0.1x for Ca in CaCl2 for total of 20+0.1x and you want to multiply this by 1.5 so it will be 50% higher than the negative charge.
mmols negative charge is 100*0.2 = 20 for Cl in NaCl and 0.2x for the Cl in CaCl2 for total of 20+0.2x. Set these equal for the following:
1.5(20+0.1x) = 20+0.2x and solve for x = mL of 0.1M CaCl2 solution. You can go through this and you should, if for no other reason than to confirm my numbers. I obtained 200 mL of the CaCl2 so the ratio is 100 mL NaCl/200 mL CaCl2 or a ratio of 1 NaCl solution/2 CaCl2 solution. If I were you I would then plug these volumes back into the original solution and confirm that the negative charge = 50% greater than the positive charge. You may even want to try difference numbers, such as 500 mL and 1000 mL (still in the ratio of 1:2) and see if the equation holds.
in what ratio 0.2M NaCl and 0.1M CaCl2 solutions are to be mixed so that in the resulting solution, the concentration of negative ions is 50% greater than the concentration of positive ions?
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