IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: XaM!! on May 24, 2010, 11:32:48 am

Title: Indicators
Post by: XaM!! on May 24, 2010, 11:32:48 am

hey guys i need help... m havn prob with indicators in chem practicals. can anyone tell me whch indicators r used with which kind of exp?

whch indicators r used in folowng papers. plz answer all of them:
i)nov 03 ques 2 indicator?
ii)may 04 ques 1
iii)oct 05 ques 1... plz m w8in...

Title: Re: Indicators
Post by: CHEMMASTER6000 on May 24, 2010, 11:37:18 am

is this edexcel papers?

Title: Re: Indicators
Post by: XaM!! on May 24, 2010, 11:45:28 am

Cie

Title: Re: Indicators
Post by: CHEMMASTER6000 on May 24, 2010, 12:08:15 pm

hmm, thought pracs were done. unless your refering to paper 5.
anyhow .

acid natured soln would require methyl orange which has range 3 to 4

basic nature soln would require phenotheilein which has range 8 to 10  :P

Title: Re: Indicators
Post by: XaM!! on May 24, 2010, 02:14:17 pm

Thanks alot

Title: Re: Indicators
Post by: XaM!! on May 24, 2010, 02:16:02 pm

can u plz answer those pprz ques???

Title: Re: Indicators
Post by: CHEMMASTER6000 on May 24, 2010, 03:29:03 pm

which papers are they? p1 p2 p3 p4 p5?

Title: Re: Indicators
Post by: XaM!! on May 24, 2010, 03:35:13 pm

Quote from: inverse tangent graph on May 24, 2010, 03:29:03 pm

which papers are they? p1 p2 p3 p4 p5?

p3

Title: Re: Indicators
Post by: CHEMMASTER6000 on May 25, 2010, 03:17:03 am

UMM dude its passed already.  :o

Title: Re: Indicators
Post by: Chingoo on May 25, 2010, 09:17:25 am

Actually, they haven't passed already. There are in total four practical papers and as far as I know, 33 has it's Physics today and 34 is yet to test for all exams.

I'm not referring to a particular practical question, but the rules for choosing an indicator are:
1) If the titration is between a weak base and strong acid, use methyl-orange/screened methyl-orange indicator.
2) If the titration if between a strong base and weak acid, use phenolphthalein indicator.
3) If the titration is between a strong base and strong acid, you can use either indicator.

I'm not sure for a weak base and weak acid, but I believe that is beyond the scope of our practicals.

Title: Re: Indicators
Post by: XaM!! on May 25, 2010, 09:41:40 am

@chingo any idea wats coming in practical? iv heard iodometry?

Title: Re: Indicators
Post by: Chingoo on May 25, 2010, 09:50:41 am

Nope, I have no idea.

Title: Re: Indicators
Post by: XaM!! on May 25, 2010, 10:05:08 am

Oh ok. :-(

Title: Re: Indicators
Post by: chocoholic-me on May 25, 2010, 01:01:22 pm

good sites for last minute revision .. i found them helpful :)

http://spark000.blogspot.com/ (http://spark000.blogspot.com/)