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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 344815 times)

Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2655 on: June 05, 2010, 08:44:14 pm »
Quote from: rhea on June 05, 2010, 08:32:22 pm
what about nitrite?

nd sulphite and carbntes of ONLY NA and K do not decompose?

Nitrates of Na and K decompose, but in a different way.. products are different

2 Zn(NO3)2  ----> 2ZnO  + 4 NO2 + O2

2 KNO3  ----> 2 KNO2   +  O2

Hg(NO3)2  ---->  2Hg  +  2NO2  +  O2

2AgNO3  ----> 2Ag  +  2 NO2  +  O2


Yup only Na and K

okay, not sure about nitrites, because they are formed by the decomposition of (K, Na)nitrates itself..
« Last Edit: June 06, 2010, 06:39:50 am by ~VIN1094~ »
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Offline CatAly$t

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2656 on: June 05, 2010, 08:54:29 pm »
Quote from: Shooting Star on June 05, 2010, 08:22:12 pm

this answers ur question catalyst

thx girl... :D

also mohit man...
« Last Edit: June 05, 2010, 08:56:55 pm by CatAly$t »
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InshaAllah 8 A* in IGCSE....Ameen.....

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Offline Allyza1n

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2657 on: June 05, 2010, 09:15:45 pm »
hey...

Could someone plzz answer question 5 b from chemistry 2009 may june variant one....
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2658 on: June 05, 2010, 09:20:48 pm »
Quote from: Allyza1n on June 05, 2010, 09:15:45 pm
hey...

Could someone plzz answer question 5 b from chemistry 2009 may june variant one....

here you go

https://studentforums.biz/index.php/topic,1411.msg249826.html#msg249826
« Last Edit: June 05, 2010, 09:24:11 pm by ~VIN1094~ »
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Offline NidZ- Hero

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2659 on: June 05, 2010, 09:39:08 pm »
HEATING HYDROXIDES
Sodium hydroxide and potassium hydroxide are NOT CHANGED by heating
them.
Calcium hydroxide and magnesium hydroxide behave in the same way.
HYDROXIDE + HEAT = OXIDE + WATER
Ca(OH)2(aq) = CaO(s) + H2O(l)
Mg(OH)2(aq) = MgO(s) + H2O(l)
Iron (III) hydroxide is also decomposed by heating to form iron (III) oxide and
water.
2Fe(OH)3(s) = Fe2O3(s) + 3H2O(l)
HEATING NITRATES
Group 1 nitrate + heat = group 1 nitrite + oxygen gas
2NaNO3(s) = 2NaNO2 + O2(g)
2KNO3(s) = 2NKNO2 + O2(g)
All other nitrates behave in the same way when heated
NITRATE + HEAT = OXIDE + NITRITE + OXYGEN GAS
2Ca(NO3)2 = 2CaO(S) + 4NO2(g) + O2(g)
2Cu(NO3)2 = 2CuO(S) + 4NO2(g) + O2(g)
2Zn(NO3)2 = 2ZnO(S) + 4NO2(g) + O2(g)
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Offline NidZ- Hero

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2660 on: June 05, 2010, 09:46:58 pm »
Quote from: ~VIN1094~ on June 05, 2010, 07:54:11 pm
Hydrogen Sulfide = H2S

H - 1
S - 2, 8, 6

would be something like..

                     oo
                o           o
            H        S           H
                x            x
                      oo

thanz pal :)
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Offline sarasa

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2661 on: June 05, 2010, 11:43:00 pm »
Quote from: Nidzzz on June 05, 2010, 09:39:08 pm
HEATING HYDROXIDES
Sodium hydroxide and potassium hydroxide are NOT CHANGED by heating
them.
Calcium hydroxide and magnesium hydroxide behave in the same way.
HYDROXIDE + HEAT = OXIDE + WATER
Ca(OH)2(aq) = CaO(s) + H2O(l)
Mg(OH)2(aq) = MgO(s) + H2O(l)
Iron (III) hydroxide is also decomposed by heating to form iron (III) oxide and
water.
2Fe(OH)3(s) = Fe2O3(s) + 3H2O(l)
HEATING NITRATES
Group 1 nitrate + heat = group 1 nitrite + oxygen gas
2NaNO3(s) = 2NaNO2 + O2(g)
2KNO3(s) = 2NKNO2 + O2(g)
All other nitrates behave in the same way when heated
NITRATE + HEAT = OXIDE + NITRITE + OXYGEN GAS
2Ca(NO3)2 = 2CaO(S) + 4NO2(g) + O2(g)
2Cu(NO3)2 = 2CuO(S) + 4NO2(g) + O2(g)
2Zn(NO3)2 = 2ZnO(S) + 4NO2(g) + O2(g)
NITRATE + HEAT = OXIDE + NITROGEN DIOXIDE + OXYGEN GAS
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Offline Raywin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2662 on: June 06, 2010, 03:35:26 am »
Quote from: ~VIN1094~ on June 05, 2010, 08:44:14 pm
Nitrates of Na and K decompose, but in a different way.. products are different

2 Zn(NO3)2  ----> 2ZnO  + 4 NO2 + O2

2 KNO3  ----> 2 KNO2   +  O2

Hg(NO3)2  ---->  2Ag  +  2NO2  +  O2

2AgNO3  ----> 2Ag  +  2 NO2  +  O2


Yup only Na and K

okay, not sure about nitrites, because they are formed by the decomposition of (K, Na)nitrates itself..

Hey Vin,
Hg(NO3)2  ---->  2Ag  +  2NO2  +  O2     Where did the Ag come from?  ??? lol isnt it supposed to be Hg? :P
« Last Edit: June 06, 2010, 03:39:08 am by Raywin »
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2663 on: June 06, 2010, 06:39:27 am »
Quote from: Raywin on June 06, 2010, 03:35:26 am
Hey Vin,
Hg(NO3)2  ---->  2Ag  +  2NO2  +  O2     Where did the Ag come from?  ??? lol isnt it supposed to be Hg? :P

Oh sorry dude. I was in a hurry... :-[
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Offline Raywin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2664 on: June 06, 2010, 07:02:51 am »
Quote from: ~VIN1094~ on June 06, 2010, 06:39:27 am
Oh sorry dude. I was in a hurry... :-[

Hahaha, np. :D
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Offline Raywin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2665 on: June 06, 2010, 08:01:58 am »
Guys, in polymers, whts a Single repeating unit? ??? Thanks a lot.. :D
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2666 on: June 06, 2010, 08:03:11 am »
Quote from: Raywin on June 06, 2010, 08:01:58 am
Guys, in polymers, whts a Single repeating unit? ??? Thanks a lot.. :D

"monomer "

they repeat to form a long chaine  macromelecule ( polymer )
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Offline Raywin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2667 on: June 06, 2010, 08:04:48 am »
Quote from: Kimo Jesus on June 06, 2010, 08:03:11 am
"monomer "

they repeat to form a long chaine  macromelecule ( polymer )

But doesn't that happen in any other polymer? ??? Thanks :)
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2668 on: June 06, 2010, 08:10:26 am »
Quote from: Raywin on June 06, 2010, 08:04:48 am
But doesn't that happen in any other polymer? ??? Thanks :)

monomers are in all polymers < everything has a different monomer

poly ( ETHEENE ) has ethene monomer
poly ( propene ) has propmene monemer 

ethene and propene are the repeating units


in the case  CONDESATION polymerisation

there is a repeating unit for nylon ( DIAMINE+ DICARBOXILYIC ACID )
there is a repeating unit for terylene (  DIOL + DICARBOXYILC ACID )
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Offline Raywin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2669 on: June 06, 2010, 08:13:47 am »
Quote from: Kimo Jesus on June 06, 2010, 08:10:26 am
monomers are in all polymers < everything has a different monomer

poly ( ETHEENE ) has ethene monomer
poly ( propene ) has propmene monemer 

ethene and propene are the repeating units


in the case  CONDESATION polymerisation

there is a repeating unit for nylon ( DIAMINE+ DICARBOXILYIC ACID )
there is a repeating unit for terylene (  DIOL + DICARBOXYILC ACID )

Oh, so repeating units are just monomers? Ryte :) Thanks a lot once again.. ;D
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