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

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: Greed444 on August 02, 2010, 12:30:33 am

Title: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 02, 2010, 12:30:33 am

i need help on how to answer Q4 from may/june 2007 which i cant solve.
can you show step by step especially for the harder stuff pleaseee?

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Saladin on August 02, 2010, 12:31:41 am

Can you please attach the question paper?

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 02, 2010, 01:08:23 am

i'll just give you the online link to the paper since i dont have one of my own

here it is
http://www.xtremepapers.net/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_s07_qp_4.pdf

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Saladin on August 02, 2010, 01:40:11 am

Try freeexampapers.com for papers. They have the latest ones there.

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Saladin on August 02, 2010, 01:41:53 am

I have not done this in A2 Chem yet. So very sorry.

I think Ahana can help you with it though.

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 02, 2010, 01:50:35 am

its okay man, thanks though. I'll wait for Ahana or someone who can answer this Question well.
just direct them here alright thanks

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: nid404 on August 02, 2010, 11:48:40 am

Can you be specific? Which part do you not understand?

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 02, 2010, 01:53:35 pm

Q4 part (c) its the part where the graph comes in.
im having a hard time to figure it out. could you take look at it please?

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Onion on August 02, 2010, 05:14:47 pm

The colour observed is the opposite to the colour absorbed in the complementary colour wheel

first part: the colour absorbed is blue-ish/violet - so the colour observed (opposite in the colour wheel) is orange-ish/red so answer is RED

second part: the colour absorbed is yellowish/red/orange - so colour observed would be BLUE

It's a bit confusing but yeah, I hope that helps.

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Saladin on August 02, 2010, 06:20:37 pm

+ REP

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 03, 2010, 03:20:50 am

Quote from: Onion on August 02, 2010, 05:14:47 pm

The colour observed is the opposite to the colour absorbed in the complementary colour wheel

first part: the colour absorbed is blue-ish/violet - so the colour observed (opposite in the colour wheel) is orange-ish/red so answer is RED

second part: the colour absorbed is yellowish/red/orange - so colour observed would be BLUE

It's a bit confusing but yeah, I hope that helps.

how do you read from the graph to know what colour is absorbed?
do we need to look only at the peak levels?
from C, the peak is around 460nm and D would be around 620nm?

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: nid404 on August 03, 2010, 12:16:41 pm

The color that the compound has is the color it emits....so the absorption of that color(frequency of color) would be low.

In C, absorption is low at abt 650nm, hence it emits red color
In D, absorption is low close to 450 nm, hence it emits blue color

Check the ppt attached for better understanding of how to read graphs

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Onion on August 03, 2010, 12:58:23 pm

Ah yes, that's the other way to look at and probably the easier one.

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Greed444 on August 04, 2010, 07:50:00 am

thank you all, i got it now  ;D
the ppt was very helpful thanks again

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: nid404 on August 04, 2010, 12:37:51 pm

Pleasure is mine :)

Title: Re: Need HELP on CIE Chemistry paper 4 and 5!
Post by: Freaked12 on August 04, 2010, 01:37:51 pm

+rep