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Author Topic: CHEMISTRY PAPER 1 HERE  (Read 38683 times)

Offline john12345

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Re: CHEMISTRY PAPER 1 HERE
« Reply #15 on: June 10, 2009, 03:04:58 pm »
Quote from: Tammy on June 10, 2009, 02:39:13 pm
Yes, hydrogen is produced at the negative electrode, but if you look at the solution left: it's NaOH which is basic.

   Na+         Cl-
   H+          OH-

The ones coloured red are the ones that are produced at the electrodes, and what's left is Sodium hydroxide.
hey tammy thanks a lot for ur help

i had one more doubt about this
why is the sodium hyroxide formed at the cathode, shudnt it just form anywhere in the tube

y is it specifically formed at the cathode?????

nd shudnt de hydrogen formed at the cathode make the cathode area acidic>????
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #16 on: June 10, 2009, 03:10:32 pm »
NaOH form at the cathode cause the formula is :

2H2O+2e=h2+2OH-

THERFORE HYDROXIDE IONS FORM NEAR THE CATHODE .....
THIS HYDROXIDE IONS MAKE THE INDICATOR COLOUR GOES BLUE....


hope i helped.... :)
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Offline john12345

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Re: CHEMISTRY PAPER 1 HERE
« Reply #17 on: June 10, 2009, 03:19:39 pm »
Quote from: esso on June 10, 2009, 03:10:32 pm
NaOH form at the cathode cause the formula is :

2H2O+2e=h2+2OH-

THERFORE HYDROXIDE IONS FORM NEAR THE CATHODE .....
THIS HYDROXIDE IONS MAKE THE INDICATOR COLOUR GOES BLUE....


hope i helped.... :)

hey esso
but since de hydroxide ions are negatively charged shudnt dey be attracted to the positive electrode (anode)
nd how does water gain 2 electrons, where does it get dose 2 electrons from ????

im slightly confused

i understand dat oxidation taked place at the anode with clhorine ions losing electrons to form chlroine gas

and dat reduction takes place at cathode with hydrogen ions gaining electrons from de cathode to form hydrogen gas

den what happens to the remaining sodium ions nd hydroxide ions

how come they form near the cathode???
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #18 on: June 10, 2009, 03:24:53 pm »
since the hydroxide ions form near the cathode .... they attract the sodium ions and form at the cathode.....

.....dont have to know in detail though....

water gains electrons from the cathode ,,, therefore reduction takes place as u said .....
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Offline john12345

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Re: CHEMISTRY PAPER 1 HERE
« Reply #19 on: June 10, 2009, 03:35:59 pm »
Quote from: esso on June 10, 2009, 03:24:53 pm
since the hydroxide ions form near the cathode .... they attract the sodium ions and form at the cathode.....

.....dont have to know in detail though....

water gains electrons from the cathode ,,, therefore reduction takes place as u said .....

thanks a lot esso
+ rep for u
however dude i dont get it why do de hydroxide ions form near the cathode shudnt dey be attracted to de anode dats wat i dont undersatdn
i understand dat sodium ions are formed near de cathode since dey are attracted to the cathode as they are positive ions

nd dude y does water gain 2 electrons to form hydroxide
shudnt water naturally dissociate to form the hydrogen ions and hydroxide ions

because we have never been taught about water gaining 2 electrons from de cathode to form de hydroxde ions + hydrogen

we have been told dat water dissociates to produce hydrogen ions _ hydroxide ions

nd for hydroxide weve learnt that

4OH- = 2H20 + O2 + 4 electrons

can u please help as to why water gains two electrons from the cathode?????????/
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #20 on: June 10, 2009, 03:40:55 pm »
i really donot bt dat wat r teacher told us abt,....

let nid explain it to ya he will make it simplier as i am not good in explaining though......
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Offline Blood0cean

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Re: CHEMISTRY PAPER 1 HERE
« Reply #21 on: June 10, 2009, 03:43:58 pm »
plz dont rite hope i helpd after each post with a childish smile -.-

its real degrading........
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #22 on: June 10, 2009, 03:45:21 pm »
every one has his own personal freedom..rite or i am wrong...
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #23 on: June 10, 2009, 03:47:47 pm »
-repped me rite...too many kids in this forum....
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nid404

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Re: CHEMISTRY PAPER 1 HERE
« Reply #24 on: June 10, 2009, 03:49:06 pm »
Quote from: esso on June 10, 2009, 03:40:55 pm
i really donot bt dat wat r teacher told us abt,....

let nid explain it to ya he will make it simplier as i am not good in explaining though......

im she..*with pride*...lol...no time for jokin..

The answer is D for sure as chlorine bleaches damp litmus and alkali turns universal indicator blue

I'll explain the thing...give me two minutes. I'll frame my words well to make u understand
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Offline esso

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Re: CHEMISTRY PAPER 1 HERE
« Reply #25 on: June 10, 2009, 03:50:45 pm »
but ur user name is nid rite... dats why i said nid...
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nid404

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Re: CHEMISTRY PAPER 1 HERE
« Reply #26 on: June 10, 2009, 03:59:35 pm »
Let’s first consider the ions present
H+  OH-

Na+  Cl-



what exactly happens in the solution when electricity is passed through

The negative electrode(cathode) attracts the Hydrogen ions are attracted to it. They accept electrons to form hydrogen gas(which does not produce any change in the indicator)

At the positive electrode(anode), chloride ions are attracted. Here they lose two electrons to form chlorine gas. The chlorine bleaches the indicator.

The ions remaining form sodium hydroxide but the color change to blue is observed at the other electrode only because at the anode the indicator is bleached.


Ask again if u don't understand
« Last Edit: June 10, 2009, 04:01:59 pm by nid404 »
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Offline john12345

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Re: CHEMISTRY PAPER 1 HERE
« Reply #27 on: June 10, 2009, 04:22:21 pm »
Quote from: nid404 on June 10, 2009, 03:59:35 pm
Let’s first consider the ions present
H+  OH-

Na+  Cl-



what exactly happens in the solution when electricity is passed through

The negative electrode(cathode) attracts the Hydrogen ions are attracted to it. They accept electrons to form hydrogen gas(which does not produce any change in the indicator)

At the positive electrode(anode), chloride ions are attracted. Here they lose two electrons to form chlorine gas. The chlorine bleaches the indicator.

The ions remaining form sodium hydroxide but the color change to blue is observed at the other electrode only because at the anode the indicator is bleached.


Ask again if u don't understand

oh allright got it thanx a lot nid. really nice of u to help

one more thing so de hydrogen formed at cathode doesnt affect de indicator becoz its as gas nd not as H+ ions,is dat de reason why de hydrogen gas has no effect on de indicator???

also so de sodium hydroxide is formed everywhere however it only affects the cathode region, because at the anode the litmus paper is bleached.. is dat rite
so if de litmus paper had not been bleached den even at de anode the litmus paper would have turned blue??

nd before chlroine turns damp blue litmus paper white it first turn the damn blue litmus paper red rite?? y is dat

nd one more question will sulphur dioxide gas react weith sodium hydroxide.. if yes what are the products

+ rep for u. Thanks a lot for ur help. hope im not wasting too much of ur time

which country r u from??
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Offline Petrol

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Re: CHEMISTRY PAPER 1 HERE
« Reply #28 on: June 10, 2009, 04:24:13 pm »
can u please help me.. i kinda suck at chemisty but i heard this was a CORE paper is that true?

if it is where can i find CORE notes so i can study from them?
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nid404

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Re: CHEMISTRY PAPER 1 HERE
« Reply #29 on: June 10, 2009, 04:26:09 pm »
Quote from: Petrol on June 10, 2009, 04:24:13 pm
can u please help me.. i kinda suck at chemisty but i heard this was a CORE paper is that true?

if it is where can i find CORE notes so i can study from them?

i don't think u can get notes specifically for the core syllabus. Ull have to co-relate the  matter in ur text or guide with the core syllabus
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