AS Level Chem Practical Paper 35

[Jia Yean]

Hi there!!

I'm having Chemistry practical exam (Paper 3) on the 25th of October.
Are there any tips or special techniques that can be shared?

I have a question though..-
Regarding the "maximum error".
For each burette reading, max error = 0.05 cm3 (half the smallest division)
Thus, overall max error = 2 x 0.05 = 0.10cm3 (which is also error per titration)
But recently I've come across an experiment that asks us to find the max error for EACH titre. I put 0.10cm3 as each titre would consist of 2 burette readings (hence 0.05 x 2), but my lecturer said it should be 0.05cm3 instead. I'm confused again @.@
Help..?

Thanks !!

 

[hino]

what is hydrogen peroxide used for in salt analysis or to test which cation or anion it is used.

 

[Jia Yean]

what is hydrogen peroxide used for in salt analysis or to test which cation or anion it is used.

Hino : I have never come across hydrogen peroxide in the qualitative analysis of CIE AS Level so far. I only remember using it when testing for some sort of rate of reaction experiment.

 

[hino]

hi jia,yes i know its not in the qualitative analysis but just like u said i did come across a practical in which h2o2 was added to an unknown solution of cation and anions and so i was wondering that why did we add h2o2 or what was the purpose of adding it

 

[Nishii]

what is hydrogen peroxide used for in salt analysis or to test which cation or anion it is used.

Mn2+ and Cr3+

 

[hino]

Mn2+ and Cr3+

yes this is what i wanted to confirm
Thankyou

 

[hino]

Mn2+ and Cr3+

yes this is what i wanted to confirm
Thankyou

 

[hino]

yes thats what i wanted to confirm
Thankyou

 

[Nishii]

You're welcome

 

[crisangle]

Can anyone post the download of chemistry and physics practical book so that i can download it.

 

[Nishii]

t

Hi there!!

I'm having Chemistry practical exam (Paper 3) on the 25th of October.
Are there any tips or special techniques that can be shared?

I have a question though..-
Regarding the "maximum error".
For each burette reading, max error = 0.05 cm3 (half the smallest division)
Thus, overall max error = 2 x 0.05 = 0.10cm3 (which is also error per titration)
But recently I've come across an experiment that asks us to find the max error for EACH titre. I put 0.10cm3 as each titre would consist of 2 burette readings (hence 0.05 x 2), but my lecturer said it should be 0.05cm3 instead. I'm confused again @.@
Help..?

Thanks !!

this might be helpful!! http://www.xtremepapers.com/community/threads/tips-for-chemistry-practicals-p3.11810/

 

[Jia Yean]

Mn2+ and Cr3+

May I know what do you mean by that? Is this part of qualitative analysis?
I'm a bit confused

 

[Nishii]

its a confirmatory test,

you need to add NaOH followed by H2O2, and if

1) Mn2+ is present, you get an offwhite precipitate formed which turns into a dark brown precipitate on addition of H2O2. Also effervescence occurs (oxygen is released)

2) Cr3+ is present, you get a grey green ppt which dissolves in excess to give a dark green solution, the solution turns yellow on heating with H2O2!

 

[MindStealth]

http://www.xtremepapers.com/community/threads/tips-for-chemistry-practicals-p3.11810/#post-158934