[redrob]

I am stumped and can't get the right answer for the following problem.  If you have a 10 liter solution of 10% acid, and you add 10 liters of pure acid to that then what is the concentration of acid in the solution.  My answer manual has the answer as either 45%, 45.6%, 55%,or 55.6%.  Thanks...

[dexangeles]

can you at least show us what you have done so far?

[redrob]

I was thinking that it has to be solved using log function as the dillution is a sloping occurance.  It isnt exponential and the graph should look like a plotted log.  I just have no clue how to start.  I am trying to go ahead of class and learn this so I won't get behind.  

[Borek]

Try the simplest approach - start with the concentration definition:

Cp = substance mass / solution mass * 100%

You will have to substitute volume for the mass, which is equivalent of assuming specific density = 1 g/ml.

Calculate how much acid and how much solvent is in the 10 litres of starting solution. Add 10 litres of acid - you have both quantity of acid and solvent in the final solution at hand at this moment, so you can use definition once again and lo - you are ready.

Most (if not all) concentration questions can be done this way - you start with definition and end with definition, using your built-in processor for all intermediate steps  

[redrob]

OK thanks I was over complicating things.  11L/20L=55%