Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: redrob on February 26, 2005, 06:59:18 AM
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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...
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can you at least show us what you have done so far?
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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.
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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 ;)
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OK thanks I was over complicating things. 11L/20L=55%