1. The problem statement, all variables and given/known data Determine how much distilled water must be added to 250 ml of a 1.5 M solution of Na2CO3 to dilute it to a concentraion of 0.5 M. 2. Relevant equations c1v1=c2v2 3. The attempt at a solution I'm having trouble understanding how to identify c1,v1,c2, and v2, especially since every question is worded differently. My guess is that v1 = 250mL, c1 = 1.5 M, and c2 = 0.5 M. And we're solving for v2...? My teacher didn't explain this very well so is there any rule for this law? Because for example I know that c1 and c2 can't be used interchangeably so how do I know which is c1 and which is c2?