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Topic: concentration of acid question  (Read 4074 times)

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redrob

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concentration of acid question
« on: February 26, 2005, 06:59:18 AM »
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

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Re:concentration of acid question
« Reply #1 on: February 26, 2005, 02:11:09 PM »
can you at least show us what you have done so far?
« Last Edit: February 26, 2005, 02:11:35 PM by Ad Majorem Dei Gloriam »

redrob

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Re:concentration of acid question
« Reply #2 on: February 26, 2005, 04:04:37 PM »
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.  

Offline Borek

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Re:concentration of acid question
« Reply #3 on: February 26, 2005, 06:26:54 PM »
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  ;)
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

redrob

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Re:concentration of acid question
« Reply #4 on: February 27, 2005, 08:09:36 AM »
OK thanks I was over complicating things.  11L/20L=55%

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