i have the destroyer, and i just came across a problem like that, but it didnt really explain why it used just a certain volume, the question was something like this
if you have a 50 ml of 2 M of some strong base and added it to 40 ml of some strong acid what would the concentration of the acid be. I thought I would do it like this
(50ml)(2M) = (90ml)(Mf) which was wrong the answer was to do it like this
(50)(2M) = (40ml)(M)
I guess if they ask for the molarity of SOLUTION then you would have to add the two volmes together fro the second half, but if they just ask for the concentration of a certain thing you wouldnt?