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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: kenny1999 on April 14, 2011, 10:36:45 AM

Title: 0.0020M Sulphuric acid
Post by: kenny1999 on April 14, 2011, 10:36:45 AM

I encounter a M.C. question

it asks " what is the pH of 0.002M of H2SO4 (sulphuric acid) "

At first I suppose that it is a strong acid and dibasic so it gives two H+ ion on dissociation.

so for 0.002M of the acid there should be 0.002x2 = 0.004M of H+ ion and this value
should be used to calculate the pH, which is about 2.37

However, none of the choices in the question is 2.37 so I tried using 0.002M of H+ to calculate the value, so as to assume that the sulphuric acid first dissciate to H+ and hydrogensulphate, then the correct value is obtained.

However, why and how does the question knows that it only dissciates only one H+ instead of two for each sulphuric acid molecules? They don't have any other information, only that it is a 0.002M sulphuric acid.

Title: Re: 0.0020M Sulphuric acid
Post by: DevaDevil on April 14, 2011, 10:51:42 AM

please don't cross-post.

you already asked this question here (http://www.chemicalforums.com/index.php?topic=47934.0)