[joshp1118]

I seem to have a "disagreement" with my chem professor on a simple math/molarity problem.

Question: How much water must be added to 25 ml of a 0.5M solution to prepare a 0.1M solution?

My answer is that 100ml water must be added to make a total of 125ml 0.1M solution.

His answer is add 125ml.

I've looked at this several different ways.. Am I missing something? This seems simple.

[Borek]

You are right. 125 mL is the final volume, as you start with 25 mL, you need to add 100 mL only.

[joshp1118]

Thanks friend 

[curiouscat]

If you want to be pedantic you must add enough water so that final solution is 125 ml (as Borek correctly said. ).

100 ml is practically ok, but in theory volumes may not be additive so you may have to add a tad less or more than 100 ml to make 125 ml.