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Extended Hess' Law - HSN forum

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Extended Hess' Law


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#1 d00pyd

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Posted 25 May 2006 - 09:54 AM

Hi,

I'd appreciate it if anyone could help me out with this. I've been teaching myself chem and following the syllabus set out by SQA. However ,yesterday I was reading a revision guide bought from a book shop, which claims to follow SQA. There were quite a lot of aspects following on from Hess' Law about bond breaking and making enthalpies (which were fine) but then some quite detailed stuff about this. It doesn't appear in the syllabus I have or the text book I use, which I thought was the official text (the one with the sailboat on it!!). Just wondering if there is anything beyond the standard hess law stuff that comes up on the past papers, that you would recommend I look into.

Also, anyone know where i can find a good summary of chemical tests, like what absorbs CO2, water, colour changes for sugars and all that. I didn't do standard grade so these are all a bit wobbly!

Thanks, any pointers very much appreciated on this.

#2 AM4R

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Posted 25 May 2006 - 10:35 AM

QUOTE(d00pyd @ May 25 2006, 10:54 AM) View Post

Hi,

I'd appreciate it if anyone could help me out with this. I've been teaching myself chem and following the syllabus set out by SQA. However ,yesterday I was reading a revision guide bought from a book shop, which claims to follow SQA. There were quite a lot of aspects following on from Hess' Law about bond breaking and making enthalpies (which were fine) but then some quite detailed stuff about this. It doesn't appear in the syllabus I have or the text book I use, which I thought was the official text (the one with the sailboat on it!!). Just wondering if there is anything beyond the standard hess law stuff that comes up on the past papers, that you would recommend I look into.

Also, anyone know where i can find a good summary of chemical tests, like what absorbs CO2, water, colour changes for sugars and all that. I didn't do standard grade so these are all a bit wobbly!

Thanks, any pointers very much appreciated on this.


Its just really basic hess's law that comes up in the exams i think. Mostly what it means and using the equations to find the enthalpy changes.

A good place for notes is here, and also bitesize. I hope that sorta helps!

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#3 d00pyd

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Posted 25 May 2006 - 11:10 AM

Thanks for that! I think you're right from the past papers Hess' Law is pretty straigtforward (famous last words!!). This site is very good, and I'll have a look at bitesize too. But what I really want is a nice list of all the tests we're expected to know - empty plate waiting here!! I suppose I should make my own! The ones that throw me are the simple ones, for example when you set up experimental apparatus and need to get rid of Carbon dioxide etc. Sometimes I see apparatus with tubes going into water and then a test tube collecting gases - why do they do this??

This is what comes from not doing practicals!!



#4 Pammy

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Posted 25 May 2006 - 11:14 AM

If you go here you will find a list of expected PPA questions that may help a little

http://www.hsn.uk.net/forum/index.php?showtopic=377

I don't know if it's what you need, but it is very good smile.gif
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#5 d00pyd

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Posted 25 May 2006 - 11:17 AM

QUOTE(Pammy @ May 25 2006, 12:14 PM) View Post

If you go here you will find a list of expected PPA questions that may help a little

http://www.hsn.uk.net/forum/index.php?showtopic=377

I don't know if it's what you need, but it is very good smile.gif


Thank you!! Much appreciated - it's excellent. Now all we need is for those questions to pop up. Wish i had found this site before my biology!

#6 **Bernadette**

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Posted 25 May 2006 - 11:31 AM

Here is a wee list of some tests, I don't know if this will be useful.

A solid being formed when two solutions are added is called precipitation.
The test for oxygen is that it relights a glowing splint.
The test for carbon dioxide is that it turns limewater milky.
A test for water is that cobalt chloride paper changes from blue to pink in its presence or that it boils at 100 degrees and freezes at 0 degrees.

General Equations for reactions with acids

acid+metal implies.gif salt + hydrogen
acid+metal oxide implies.gif salt +water
acid +alkali implies.gif salt +water
acid+ metal carbonate implies.gif salt+carbon dioxide +water

Reactions of Metals

metal+ oxygen implies.gif metal oxide
metal + water implies.gif metal hydroxide +hydrogen
metal +acid implies.gif salt + hydrogen

The test for starch is that it turns iodine solution from brown to blue/black.
The test for gluscose/fructose/maltose but NOT SUCROSE is that it turns Benedict's solution from blue to orange.

#7 d00pyd

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Posted 25 May 2006 - 11:37 AM

smile.gif smile.gif smile.gif

You're all so helpful thank you!! Perhaps I could get someone to do the exam for me! No one checked any id at the college I sat Biology Higher at!! Except maybe you'll all be doing the exam for yourselves .. damm!

#8 dfx

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Posted 25 May 2006 - 04:13 PM

Careful not to revise from a textbook for the english A levels, they go way indepth with Hess's law.





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