[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!

[MrTeo]

Here's something that could be quite useful to you: M stands for molarity, m is the molality (m_solvent and m_solute are the masses), M_r is the molecular mass (relative) and the density.



The units used are g/L for the density (even if dividing it by 1000 in the last passage we convert it to g/cm³), grams and liters for volume.

[Borek]

Printable, downloadable concentration cheat sheet.

Mass of solvent - assuming diluted solutions it is just volume times density (1 g/mL for water).