[chmry]

Ok so I'm suppose to calculate how many milliliters of the solute (ethylene glycol) and the solvent (tert-butanol) i should use to make a 20mL solution which has a molality of 1m. I've searched all over the internet and can't seem to find a similar problem.

[Arkcon]

Well, its possible you tried and had astounding poor luck, but there must be a thousand threads on this forum alone on how to make solutions.

First of all, do you mean a solution of 20 m, or 20 M?  Sorry, but each abbreviation has a separate definition.  When you determine which one you really mean, which you did say was molality (m), can you use the definition of the term to begin to solve this problem?

Sorry to answer a question with a question, but that's how we help here on the Chemical forums.  Its all in the Forum Rules{click}

[chmry]

Yes, i meant molality. I saw a similar problem where it was the opposite (calculate molality given volume.) and I tried to work backwards but failed.

[chmry]

Also i meant 20 milliliters of a solution which has 1m.

[Borek]

Would knowing mas of the solution help? How do you convert between volume and mass?

[chmry]

You use the density right? But what if you have two different densities in the solution?

[Borek]

The only density that you need is the density of the mixture. You can express the amounts of liquids needed to prepare the solution as masses, and that'll be an exact answer.

If you don't know the density of the mixture you have to look for an approximation. Unfortunately, volumes are not additive, so it is not possible to precisely calculate the density of the mixture, even if you know densities of the components. However, in most cases errors introduced by assuming volumes ARE additive are small enough to be negligible (especially when you are aiming at a solution that is 1 m, and not 1.0000 m).

[AWK]

ensity of pure ethylene glycol is also needed (answer in volume is needed), but this can be find in Wikipedia.
For 1 molal concentration the density of solution may be approximated by density of solvent - my guess - a few percent error (in fact about 2%).