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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 330562 times)

Offline CatAly$t

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #765 on: May 15, 2010, 08:03:44 pm »
Quote from: ~VIN1094~ on May 15, 2010, 08:01:10 pm
to decompose compounds which might be useful as elements or in simpler forms .. y do u ask ?

just curious...we dont have to know it?
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #766 on: May 15, 2010, 08:05:55 pm »

ofc we do .. jus askin .. i thought u;d seen in some past paper or somethin .. because normally they dont ask such stuff .. =)
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Offline K_M

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #767 on: May 15, 2010, 08:06:20 pm »
I have a doubt and i've no idea from where i got this idea but please tell me if i'm right..
In most questions for paper 6 (chemistry) they ask what type of reaction occured. How do we know if a reaction is exothermic or endothermic if no information about temperature change is given? Also, are all reacctions with hydrogen as a by-product exothermic? What about water? There was a question: what reaction occurs when ammonium chloride reacts with water. I thought it was exothermic and so did my colleagues but the marking scheme says endothermic. Please explain!
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nid404

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #768 on: May 15, 2010, 08:24:33 pm »
All combustion and neutralization reaction are exothermic.

When salts dissolve, an endothermic reaction occurs.

This is the general thing you need to know for igz
« Last Edit: May 15, 2010, 08:32:23 pm by nid404 »
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #769 on: May 15, 2010, 08:29:33 pm »
combustion produces heat right .. ???

my sir had told me something vital about it .. i forgot !! :(
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Offline Baladya

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #770 on: May 15, 2010, 08:31:52 pm »
Quote from: K_M on May 15, 2010, 08:06:20 pm
I have a doubt and i've no idea from where i got this idea but please tell me if i'm right..
In most questions for paper 6 (chemistry) they ask what type of reaction occured. How do we know if a reaction is exothermic or endothermic if no information about temperature change is given? Also, are all reacctions with hydrogen as a by-product exothermic? What about water? There was a question: what reaction occurs when ammonium chloride reacts with water. I thought it was exothermic and so did my colleagues but the marking scheme says endothermic. Please explain!

||Exothermic Reactions:
1) When Dilute hydrochloric acid reacts with sodium hydroxide solution a neutralistation reaction happens
2)All Displacement Reactions :
     Mg + H2SO4 ----->  MgSO4 + H2
3) Combustion

||Endothermic Reactions:
1) N2 + 02 -----> 2NO
(dunno what is it called but thats whats written in the book)
2)Thermal Decomposition:
    Ca(OH)2  ----->  CaO + H20
    2Cu (NO3)2  ------> 2CuO + 4NO2 + O2
3) Melting of ice and evaporation of water
(yes, you probably thought it was exo like me, but it turned out to be endo)
« Last Edit: May 15, 2010, 08:38:33 pm by Baladya »
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nid404

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #771 on: May 15, 2010, 08:32:09 pm »
sorry exothermic...i edited my post
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Offline haris94

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #772 on: May 15, 2010, 08:33:10 pm »
Quote from: nid404 on May 15, 2010, 08:24:33 pm
All combustion and neutralization reaction are endothermic.

When salts dissolve, an endothermic reaction occurs.

This is the general thing you need to know for igz

arent combustion reactions exothermic?  ???
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Offline haris94

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #773 on: May 15, 2010, 08:34:09 pm »
Quote from: nid404 on May 15, 2010, 08:32:09 pm
sorry exothermic...i edited my post

oops didnt see
sorry  :)
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #774 on: May 15, 2010, 08:46:36 pm »
Quote from: Baladya on May 15, 2010, 08:31:52 pm

||Endothermic Reactions:
1) N2 + 02 -----> 2NO
(dunno what is it called but thats whats written in the book)


3) Melting of ice and evaporation of water
(yes, you probably thought it was exo like me, but it turned out to be endo)


LOL Nitrogen monoxide

i knew melting of ice and evaporation of water is endothermic .. !! =P
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nid404

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #775 on: May 15, 2010, 08:51:42 pm »
How can melting and evaporation be exo  :o

It's endo..

Reason---> It gains kinetic energy, which implies heat energy also increases. To melt a substance, you supply heat...heat is taken in from the surrounding.
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #776 on: May 15, 2010, 09:01:16 pm »

.. to overcome the inter-molecular force and the molecules are set free .. its by-heart .. lol =D

but who said its exo ??
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Offline Baladya

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #777 on: May 15, 2010, 09:03:06 pm »
lol guess m srry for saying its exo xD ;D I just thought that it became hotter and so exo :P
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #778 on: May 15, 2010, 09:05:31 pm »
dont think too much !! lol .. joke =P
« Last Edit: May 15, 2010, 09:54:45 pm by ~VIN1094~ »
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Offline High-R

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #779 on: May 15, 2010, 09:45:23 pm »
nid404
can u please tell me wats all important in these chaps:homeostasis...and hormones...and drugs(which ones and wat all about them)??
i jus want u tell all thts important in brief...and explain sum hard stuff..like u did about tht lymphatic system previously!!...Thanks plz reply soon!!

tell also which papers to do?.....and which tests and expeiments to remember..like really nicely!!!...=D
thnksss sooooooo much!!..i hope u help me!!.... :)
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