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

Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: holtadit on March 20, 2010, 06:40:05 am

Title: Precipitates question
Post by: holtadit on March 20, 2010, 06:40:05 am

A 3cm3 sample of a solution of the nitrate of metal Q , concentration 1 mol/dm3, was added to 2cm3 of potassium fluoride, conc. = 1mol/dm3.

When the precipitate settled its height was measured. The experiment was then repeated using different volumes of potassium fluoride solution.

A diagram is displayed with the question. It shows that at 6cm3 the precipitates height stops increasing.


What is the formula of the fluoride of metal Q ??

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I got QF2... what do u get and please show your methid

Title: Re: Precipitates question
Post by: nid404 on March 20, 2010, 06:45:13 am

It'll be good if u name the paper......so there's no confusion :)

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:03:52 am

1990 :D

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:08:17 am

Here ya go

Title: Re: Precipitates question
Post by: nid404 on March 20, 2010, 07:16:15 am

QF₂ is what i get too

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:17:12 am

Awesome !!!

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:23:38 am

I know I m probably troubling you right now, but please please could u post your method.

Thank you Nid !!!

Title: Re: Precipitates question
Post by: nid404 on March 20, 2010, 07:27:46 am

No prob

the height of the ppt stops increasing after 6cm3....so this is the max moles of ppt that caan be formed with 3cm3 of metal nitrate

3cm3 of QNO3= 3X10^-3 moles
6cm3 of KF= 6X10^-3 moles

ratio 1:2

hence QF2

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:33:59 am

Thanks Nid... same method i used ! I would +rep u but I have to 'spread the love'  :-\

Hey, which part of India are u from ?

Title: Re: Precipitates question
Post by: nid404 on March 20, 2010, 07:43:06 am

Mumbai  ;)

Title: Re: Precipitates question
Post by: holtadit on March 20, 2010, 07:45:40 am

Cool.. i was there a few weeks ago...

Title: Re: Precipitates question
Post by: nid404 on March 20, 2010, 07:55:01 am

Quote from: Ari Ben Canaan on March 20, 2010, 07:45:40 am

Cool.. i was there a few weeks ago...

wow nice :)

what abt u??