[peter473]

Hello,

I have a chemistry exercise

If we have a solution with a volume of 15 ml (obtained from a dissolution of a solute into pure water as solvent), for which the concentration is 100%, in which we add 4 ml of pure water, then the final 19 ml solution will be at 15ml/19ml=79% right?

But now, if instead of adding 4 ml of pure water, we add 4 ml of the same solute that is at a concentration of 25%. Then, to me the final concentration will be:

(15ml + 0.25*4ml) / 19 = 84%

But I am doing it intuitively without formula
Hope this is correct
If you have corrections or better explanation would be great

Thanks for your help

Peter

[shchavel]

Hello, Peter!
You are correct.

[Meter]

You are still actually just using the formula for volume concentration, but correctly anyway. It is correct!