Molality/finding mass of solvent from known molarity of three sol'ns with same d

[warprin]

I have been looking at this for 2 hours and I'm missing something very basic.

I have three solutions: 25mL of A, 50mL of B, 100 mL of C. They all have the same solution density, which is unknown. All contain 0.041 moles of ions (aqueous ionic solution). However, I don't know what these ions are, but each solution has a particular number of ions of various charges and sizes drawn in the solutions: A has 8 ions, B has 10 ions and C has 12 ions. I calculated molarity for each at 1.64, .82 and .41 since I know the number of moles and the mass of the solution.

In trying to calculate molalities, I need the moles of solute (which I know) and the mass of the solvent, and it's the latter I'm stuck on.

Would someone point me in the right direction? I just don't see how I can calculate the mass of the solvent (even if I assume it's highly diluted and use molarity instead).

Thanks!

[kingchemist]

When you say that A has 8 ions, B has 10 ions and C has 12 ions where does this come from? Is it from a diagram as these are extremely small number of ions in any solution of volume 25mL or greater.

Remember the ions will be both positive and negative and you have the total molarity of ions. The compound might be X⁺Y^- or (X⁺)₂Y^2- or one of many other possibilities so I don't think you can calculate the molarity of the compound from this. The molarities you have calculated are based on the total number of ions in the solution (positive and negative)

Based on the number of ions (which I think are too low) A contain 8 ions/25mL, B has 5 ions/25mL and C has 3 ions/25mL

[warprin]

I follow what you did in the last sentence, normalizing the solution volume, hoping I would see something I was missing.

The ions I mentioned as far as number (8,10,12) were drawn in each of three diagrams, representing the three different solutions.

Since I was supplied the number of moles per solution and the solution volume, I can calculate molarity.

I'll keep looking at this, thanks!

When you say that A has 8 ions, B has 10 ions and C has 12 ions where does this come from? Is it from a diagram as these are extremely small number of ions in any solution of volume 25mL or greater.

Remember the ions will be both positive and negative and you have the total molarity of ions. The compound might be X⁺Y^- or (X⁺)₂Y^2- or one of many other possibilities so I don't think you can calculate the molarity of the compound from this. The molarities you have calculated are based on the total number of ions in the solution (positive and negative)

Based on the number of ions (which I think are too low) A contain 8 ions/25mL, B has 5 ions/25mL and C has 3 ions/25mL