# Gen Chem M1V1 = M2V2

#### Jay20155555

I am having some trouble recognizing when to use total volume (aka both acid and base volumes added up) for V2 versus when to just use the volume of either the acid or base for each.

#### Tebros

5+ Year Member
Do you have DAT destroyer? They have a handful of problems there that will def. help you recognize it. That and DAT bootcamp. If you have those 2, you practically are set for problems to practice on.

OP

#### Jay20155555

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?