Dilution Help: Finding the volume of water needed

[unixunited]

The objective: Acquire 60 mL of 0.1 mol Albumin. The only Albumin solution available is a 2.5 mol stock solution.

1)How many milliliters of the stock solution will you need to make the desired amount of the 0.1 M solution?
I used the C1 X V1 = C2 X V2 formula to calculate an answer of 2.4 mL

2)How many milliliters of water will be needed?
This is where I'm stuck, I am aware I need to find the mass percent of water or something, but this is the only information given to me and my instructor has not given any examples.

If anyone could point me in the right direction it would be greatly appreciated.

[Borek]

Simplest thinking yields V1 + V2 = 60 mL.

This is not 100% true, as volumes are not additive and final volume can be different from sum of volumes mixed, but as a first approximation, especially when solutions are not too concentrated, it works. So you can either use simplified approach using equation above, or answer that there is not enough information to precisely solve the question (you would need densities of all three solutions - water, 2.5 mol stock, 0.2 mol).

This is the reason why in lab you will never mix two precalculated volumes, standard procedure is to measure volume of the diluted solution and fill it up to desired final volume.

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[unixunited]

Thanks for the detailed advice, it was a great help!