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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 345760 times)

Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1185 on: May 17, 2010, 06:59:09 pm »
Quote from: A@di on May 17, 2010, 06:56:37 pm
I dont think so..because the no. of particles of Mg reacting with the acid will be the same..
ok well in nov 09

it says HIGHER TEMP CHANGES ..BUT IGNORE RATE? why??
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Offline Baladya

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1186 on: May 17, 2010, 06:59:24 pm »
Quote from: bulono on May 17, 2010, 06:58:01 pm
whats the difference between corrosion and rusting??


Corrosion is for any metal. Rusting is for Iron and Steel
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1187 on: May 17, 2010, 07:00:42 pm »
Quote from: Baladya on May 17, 2010, 06:51:36 pm
Can anyone plz tell me wtf is the diff between Galvanising and Sacrificial protection????  >:(
Thank you :)

Galvanised steel is steel coated with zinc. The zinc coating stops water and oxygen from reaching the steel. But even when the zinc is scratched, the steel underneath will not rust. So there must be another way in which the zinc protects the steel. This is Sacrificial Protection.

Zinc is more reactive than iron. A more reactive metal loses eelectrons and forms positive ions more easily than a less reactive metal. When the layer of zinc is scratched, a sort of electrochemical cell is set up in the presence of moisture. The electrons flow from the zinc to the iron. The zinc is oxidized and thus corrodes rather than iron.

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Offline Shazizzzle

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1188 on: May 17, 2010, 07:02:25 pm »
Mg RIBBON with 20 cm3 of HCl - Say temperature difference 15 deg. C
Mg POWDER with 20 cm3 of HCl - Temp difference greater than 15 deg. C. MAY be double. Not necessarily. BUT MORE TEMP DIFF.

4g Mg + 20 cm3 of HCL - say temp diff 15 deg. C.
8g Mg + 20 cm3 of HCl - DOUBLE temp diff - 30 deg. C

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Offline SNA

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1189 on: May 17, 2010, 07:03:20 pm »
Quote from: Baladya on May 17, 2010, 06:57:52 pm
Anyone ?

i think both are the same.
its just that galvanizing does not require electrochemical deposition.

:D
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Offline DEGO

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1190 on: May 17, 2010, 07:03:43 pm »
Quote from: Kimo Jesus on May 17, 2010, 06:52:49 pm
IF ITS LESS SOLUBE IT MEANS THAT IT DISSOLVES AT HIGHER TEMPERATURES.

THEREFORE WHEN YOU COME TO COOL IT DOWN... IT CRYSTALLISES AT HIGHER TEMPERATURE ..THATS WHY ITS ABOUVE!! CZ CRYSTALS APPEARS AT HIGHER TEMPERATURES


SI?
man i dont understand expirment really XD cn u give it a quick explanation
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Offline Baladya

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1191 on: May 17, 2010, 07:03:51 pm »
Quote from: A@di on May 17, 2010, 07:00:42 pm
Galvanised steel is steel coated with zinc. The zinc coating stops water and oxygen from reaching the steel. But even when the zinc is scratched, the steel underneath will not rust. So there must be another way in which the zinc protects the steel. This is Sacrificial Protection.

Zinc is more reactive than iron. A more reactive metal loses eelectrons and forms positive ions more easily than a less reactive metal. When the layer of zinc is scratched, a sort of electrochemical cell is set up in the presence of moisture. The electrons flow from the zinc to the iron. The zinc is oxidized and thus corrodes rather than iron.



In other words, Galvanising is coating it, and Sacrificial is the process after the coating is removed...
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1192 on: May 17, 2010, 07:04:06 pm »
mention impermeable and protective layer

ZINC OXIDE
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1193 on: May 17, 2010, 07:06:52 pm »
Quote from: Shazizzzle on May 17, 2010, 07:02:25 pm
Mg RIBBON with 20 cm3 of HCl - Say temperature difference 15 deg. C
Mg POWDER with 20 cm3 of HCl - Temp difference greater than 15 deg. C. MAY be double. Not necessarily. BUT MORE TEMP DIFF.

4g Mg + 20 cm3 of HCL - say temp diff 15 deg. C.
8g Mg + 20 cm3 of HCl - DOUBLE temp diff - 30 deg. C


wrong..just a faster rate..but same final temp
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Offline Shazizzzle

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1194 on: May 17, 2010, 07:08:22 pm »
Quote from: Kimo Jesus on May 17, 2010, 07:06:52 pm
wrong..just a faster rate..but same final temp

Yeah! Umm, that was supposed to be a question!
I forgot to write, 'please correct if wrong'. :P
Thanks! ;)
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1195 on: May 17, 2010, 07:08:53 pm »
Quote from: DEGO on May 17, 2010, 07:03:43 pm
man i dont understand expirment really XD cn u give it a quick explanation
imagine dissolving something very solubel in water and heating!..it will dissolve early at 20 * c

imagine dissolivng soemthin not so soluble in water and heating..it will disolve late at 40 *

now imagine the temp is 100* when cooling down..which 1 will appear first..the less soluble !!!!!! get it?
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NO secrets to SUCCESS , it is the result of 1.HARD WORK 2.GOOD PREPARATION 3.LEARNING FROM FAILURE
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Offline SNA

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1196 on: May 17, 2010, 07:09:29 pm »
Quote from: Baladya on May 17, 2010, 06:52:39 pm
Heating is to give it energy to the boiling point. Warming is little energy

No srry wait. Heating is to give it lots of energy (like about 70 or warever) but warming is little (like maybe 20C) u get what i mean?

so how do we know when to use warm or when to use heat?
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1197 on: May 17, 2010, 07:10:05 pm »
Quote from: Kimo Jesus on May 17, 2010, 07:06:52 pm
wrong..just a faster rate..but same final temp

so....greater/higher temp. change, they mean the final temperature rite??
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Offline DEGO

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1198 on: May 17, 2010, 07:11:36 pm »
Quote from: Kimo Jesus on May 17, 2010, 07:08:53 pm
imagine dissolving something very solubel in water and heating!..it will dissolve early at 20 * c

imagine dissolivng soemthin not so soluble in water and heating..it will disolve late at 40 *

now imagine the temp is 100* when cooling down..which 1 will appear first..the less soluble !!!!!! get it?
yh Thank You man i was thinking about it (i hate tht teacher made ms cn u upload me the original if u got it?)
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Offline bulono

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1199 on: May 17, 2010, 07:11:49 pm »
yeh if the surface area increases the final temperature after a specific time must not change.....example if we use Mg ribbon and the temp difference after 2 minutes is 15...for Mg powder it will be more than 15 as rate of reaction increases

but after all Mg is used up and if the mass of Mg is equal in both experiments the final temp wont change....
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