POST ALL CHEMISTRY QUESTIONS HERE

[Muhammad Talha]

why not oxygen???

 

[abcde]

In the electrolysis of aqueous sodium chloride which gas will be given off on the anode???

Oxygen will be given off. Chlorine is given off only when concentrated aqueous sodium chloride is electrolysed.

 

[Muhammad Talha]

thnx to both....i got it...

 

[abcde]

The exact same question is asked in May/June 2005 ATP paper. If you're doing that one, let me warn you beforehand that the mark scheme answer is incorrect! Since the word 'concentrated' is NOT mentioned in reference to aqueous sodium chloride, oxygen is released at the anode and not chlorine.

 

[vishal]

Abcde..........plz answer my qustion.....

 

[abcde]

Hey guys plzz tell me what is redox titration???? And plzz tell me the year of any ATP past paper in which redox titration came??! Plz it's urgent.......

Check question 9 of this paper: http://www.xtremepapers.me/CIE/Cambridg ... 3_qp_4.pdf
As the name suggests a redox titration involves a redox reaction! I can give you this example: an oxidising agent is added from a burette into a conical flask containing ions that can be oxidised e.g. Fe(II) ions can be oxidised to Fe(III) ions. Check that question and attempt it. That'll help.
Sorry for the late reply.

 

[Silent Hunter]

In the electrolysis of aqueous sodium chloride which gas will be given off on the anode???

Oxygen will be given off. Chlorine is given off only when concentrated aqueous sodium chloride is electrolysed.

BUT THEY DID NOT MENTION DILUTE EITHER

 

[zain786]

dudes and dudets i need help!

u know wen u get a graph in mcq's of chem p6. they give u 2 curves ending at the same level, wat does that indicate??
also how does the concentration, no. of moles, catalyst make a graph alter???
(if u guyz have images attachments plz do share them also)
thnx

it wud be better if u cud post the link of such questions or atleast the years... maybe more of us cud help dat way.

NOVEMBER 09 PAPER 4 CHEMISTRY 5070

 

[Silent Hunter]

ZAIN U TALKING ABOUT QUESTION 6?

 

[adnanj]

In the electrolysis of aqueous sodium chloride which gas will be given off on the anode???

Oxygen will be given off. Chlorine is given off only when concentrated aqueous sodium chloride is electrolysed.

BUT THEY DID NOT MENTION DILUTE EITHER

when they just say AQUEoUS.. we take it as DILUTE.

 

[adnanj]

Can anyone tell if in this paper, Q2 c ii , can we use potassium dichromate?? ms says sodium chromate only
http://www.xtremepapers.me/CIE/Cambridg ... _qp_42.pdf

 

[Muhammad Talha]

when they just say AQUEoUS.. we take it as DILUTE.

Correct.....!!

 

[Maleeha]

dudes and dudets i need help!

u know wen u get a graph in mcq's of chem p6. they give u 2 curves ending at the same level, wat does that indicate??
also how does the concentration, no. of moles, catalyst make a graph alter???
(if u guyz have images attachments plz do share them also)
thnx

it wud be better if u cud post the link of such questions or atleast the years... maybe more of us cud help dat way.

NOVEMBER 09 PAPER 4 CHEMISTRY 5070

if its q.6.. (a) is incorrect bcuz in experimnt 1 more no. of moles i.e. more amount of acid is used as calcium carbonate is in excess so increasing acid wud increase the amount of product evolved.
(b) using finely powdered CaCO3 should have made 3rd curve steeper, but 1st one is steep so this means itx rate of reaction was faster...not 3rd's.
(c) the correct one.. here total amount of product evolved is same this means moles are same only the rate is different, in one products formed quicker than the other.
(d) 3rd is less steep than 2nd, which means that possibly conc. of acid used in 2nd was greater than exp. 3.
hope it wud b helpful

 

[Maleeha]

when they just say AQUEoUS.. we take it as DILUTE.

Correct.....!!

is it confirmed?? cuz one of my tchr said dat dilute isnt mentioned n the other said concentratd wouldnt b mentioned...posting.php?mode=quote&f=25&p=85094#http://www.xtremepapers.me/forums/posting.php?mode=quote&f=25&p=85094#

 

[leosco1995]

I am confused. Some people say chlorine, some say oxygen and others say that both are acceptable when its an aqueous solution..

 

[abcde]

Can anyone tell if in this paper, Q2 c ii , can we use potassium dichromate?? ms says sodium chromate only
http://www.xtremepapers.me/CIE/Cambridg ... _qp_42.pdf

Yes, you can!

 

[abcde]

I am confused. Some people say chlorine, some say oxygen and others say that both are acceptable when its an aqueous solution..

I'm quite sure that when they say aqueous sodium chloride is electrolysed, oxygen would be released at the anode. Only if its concentrated, chlorine would be released. This is because for anions, the ease of discharge increases like this: chloride ion --> bromide ion---> iodide ion ---> hydroxide ion. So if an aqueous solution contains both chloride and hydroxide ions, hydroxide ions would be discharged, thereby producing oxygen. Secondly, an increase in the concentration of an anion tends to promote its discharge so chloride ions would be discharged only if concentrated is mentioned. Look out for this word: concentrated!

 

[xhizors]

listen all it is confirmed, if solution is only aq mean only aq is written it only means concentrated and examiner will always mention for dilute solution that electrolysis of dilute HCL in this case +ve oxygen, as solvent concentration is high means (water) and at -ve hydrogen will evolve and in test i observed that u have to insert the splinter inside the tube for both tests

 

[Maleeha]

Q6) Water containing a little dilute sulphuric acid was electrolysed, using carbon electrodes.
If 20 cm3 of oxygen were produced, what was the volume of hydrogen produced?
(a) 10 cm3
(b) 20 cm3
(c) 30 cm3
(d) 40 cm3
i noe itx answer is 40 bt i cant convince myself enuf how i came up wid this answer.. cud any1 help??

 

[xhizors]

Q6) Water containing a little dilute sulphuric acid was electrolysed, using carbon electrodes.
If 20 cm3 of oxygen were produced, what was the volume of hydrogen produced?
(a) 10 cm3
(b) 20 cm3
(c) 30 cm3
(d) 40 cm3
i noe itx answer is 40 bt i cant convince myself enuf how i came up wid this answer.. cud any1 help??

ratio 2:1 as H2O

twice hydrogen as oxygen