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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: HusamEddin on January 03, 2013, 08:34:10 AM

Title: Titration
Post by: HusamEddin on January 03, 2013, 08:34:10 AM

Hi there :)
if we have a sample of .1 grams
this sample contains Mg(OH)2
the Mg(OH)2 in the sample has been titrated by 10ml of .08M HCl
calculate the percentage of Mg(OH)2 in the sample

I suggest the answer would be like the following:
number of moles of HCl is
.08X10/1000 = .0008 mole
one mole of Mg(OH)2 is titrated by 2 moles of HCl
So at the end point , Mg(OH)2 will has half the number of moles of HCl , ie>>.0004 mole
mass = #moles * molar mass
= .0004 * 58 = .0232 grams

percentage = .0232/.1 *100% = 23.2%


is it all right like that ? because some people told me that my answer is totally wrong !!!
help :(

Title: Re: Titration
Post by: Hunter2 on January 04, 2013, 01:25:17 AM

I would say its ok.

Title: Re: Titration
Post by: ironnica on January 04, 2013, 11:07:53 AM

It all looks good. To get a more accurate answer, I would use gmm of 24.3g/mol instead of 24 but that would not put your answer off by much in comparison to what I assume you've been told.

Did you titrate the whole lot of the sample against HCl or just take some of the sample (i.e. taking some of a known volume of solution)?

Title: Re: Titration
Post by: HusamEddin on January 05, 2013, 11:49:20 AM

didn't got your question  :-\