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Anne Marie Helmenstine, Ph.D.

Understanding Volume Percent Concentration (v/v %)

By September 7, 2010

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Volumetric flasks are used to prepare volume percent solutions. (TRBfoto/Getty Images)One of the simplest yet most confusing units of concentration is volume percent or volume-volume percent (v/v %). It is very easy to prepare a chemical solution using volume percent, but if you misunderstand the definition of this unit of concentration, you'll experience problems.

Volume percent is defined as:

v/v % = [(volume of solute)/(volume of solution)] x 100%

Note that volume percent is relative to volume of solution, not volume of solvent. This is the key! For example, wine is about 12% v/v ethanol. This means there are 12 ml ethanol for every 100 ml of wine. It is important to realize liqud and gas volumes are not necessarily additive. If you mix 12 ml of ethanol and 100 ml of wine, you will get less than 112 ml of solution.

As another example, 70% v/v rubbing alcohol may be prepared by taking 700 ml of isopropyl alcohol and adding sufficient water to obtain 1000 ml of solution (which will not be 300 ml). Volumetric flasks are great for this. Add your solute, then dilute to the mark with the solvent. If you need to know how many milliliters or grams of solvent you added you can keep track by dispensing the solvent with a biuret. Temperature comes into play when preparing a volume percent solution, so it's a good idea to either aim for a relatively constant lab temperature or note the temperature when then solution was prepared.

Other Ways to Calculate Concentration | Chemistry Lab Techniques

Comments

January 2, 2011 at 5:34 pm
(1) Bryan says:

thank you, this was very helpful and what i needed

February 16, 2011 at 12:19 am
(2) H2ochick says:

U ROCK! Thanks for that dead on, head on definition!!

April 2, 2012 at 5:49 pm
(3) Dan says:

Thanks! Excellent info. So simple yet so confusing until i read this article

November 19, 2012 at 12:47 pm
(4) akanksha says:

Superbly confusing yet very interesting. I think u have done a brilliant job in explaining the concept. Thanks!

March 13, 2013 at 12:07 am
(5) Bob Winslow says:

Very helpful indeed but I think she meant you can use a Burette to help keep track of your additions.

August 12, 2013 at 10:09 pm
(6) clealsea says:

tks it help me a lot

September 4, 2013 at 1:58 pm
(7) Jason says:

Hello,

I think you meant something different here

|If you mix 12 ml of ethanol and 100 ml of wine, you will get less than 112 ml of solution.

Wouldn’t you be getting exactly 112 mL of solution the way it is worded? I think you meant something along the lines of:

If you mix 12 ml of ethanol and 100 ml of SOLVENT, you will get less than a 12% solution.

Even if that’s not what you meant the statement as written is wrong. Not trying to be obxnoious — I just don’t want any young chemists to be confused.

September 8, 2013 at 7:34 pm
(8) Swapna says:

After getting a tattoo done, two days later I got very small boils all over the tattoo, so the tattoo artist told me as she has used Vaseline while making the tattoo that might come out so she told me don’t use any cream now let it dry n it will be fine, I donno what to do!
There r very small small boils all over the tattoo n it’s like those pus which comes out of the boils, now it has been two days n the tattoo has dried up, donno what to do!
Could u pls help me immediately Mam?
Should I go to a doctor?

October 11, 2013 at 7:22 am
(9) Anil says:

Its confusing! Your statement 12% v/v ethanol means that the solution contains 12 ml of ethanol for every 100 ml of wine, but if you mix 12 ml of ethanol to 100 ml of wine, you will get less than 112 ml solution. As I understand, if the wine indicates 12% v/v ethanol, it means 12 ml of ethanol and 88 ml of flavor, water, and other substances. I hope you agree.

October 15, 2013 at 9:32 am
(10) lanie ann says:

This quite helpful ,,,it made me understand the lesson better but its still confusing…..hoping for more examples…. :-)

December 21, 2013 at 7:43 pm
(11) mari says:

thanks a lot. it really helped.

January 15, 2014 at 8:00 am
(12) Ravisastri says:

Thanks, you helped me to refresh my memory

February 26, 2014 at 7:26 am
(13) Abdulrasheed Tukura says:

I was so confuse before I read this your brilliant explanation, so thank you so much.

April 16, 2014 at 10:03 am
(14) Prabhu says:

thanks madam

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