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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Jon Manhattan on March 17, 2009, 01:22:38 PM

Title: Determining Percent Acid
Post by: Jon Manhattan on March 17, 2009, 01:22:38 PM

Hi there, I just have a question about calculating the percent acid of an unknown... I took a look at a thread very similar to this, but it didn't fully solve my problem.

If I have a 10.00 mL solution of Acetic Acid - HC₂H₃O₂ - whose molarity I have determined to be 0.195 M with a specific gravity of 1.0980. How do I go about finding the percent acid?

What I know is that % w/w = (mass of substance / mass of solution) x 100.

The mass of the substance would be 11.7 g:

0.195 mol A.A. x (60 g / 1 mol A.A.) = 11.7 g Acetic Acid.

I tried using the specific gravity to find a mass of 10.98:

D = M/V          1.0980 = M / 10.00 mL

but obviously dividing those two would give me a percent greater than 100:

11.7/10.98 x 100

so where did I go wrong here and what should I do? I'm guessing that my determination of the mass of the solution is incorrect... any help would be greatly appreciated!

Title: Re: Determining Percent Acid
Post by: Borek on March 17, 2009, 03:14:41 PM

0.195M - is 0.195 moles in what volume?

Title: Re: Determining Percent Acid
Post by: Jon Manhattan on March 17, 2009, 03:25:02 PM

10.00 mL

Title: Re: Determining Percent Acid
Post by: Borek on March 17, 2009, 03:48:04 PM

No. What is definition of molarity?

Title: Re: Determining Percent Acid
Post by: Jon Manhattan on March 17, 2009, 04:07:15 PM

oh, sorry haha. Molarity is the moles of solute per liter of solution...

Title: Re: Determining Percent Acid
Post by: Jon Manhattan on March 17, 2009, 04:17:58 PM

Ohhhhhhhh okay! Wow, what a careless mistake. Thank you very much, no wonder my answer was so far off.. I really appreciate it!