Physics, Chemistry and Biology: Post your doubts here!

[FATIMAH]

 

[EpicLol]

QUESTION !!
MJ 11 VARIANT 12..
NUMBER 3 WHY IS C NOT B :S PLEASE HELP :'(
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_ms_12.pdf

B is 2,5
C is 2,8,2 which is correct

 

[Maz]

are u SURE abt dat ans.....

http://wiki.answers.com/Q/Does_adding_water_change_the_pH_of_an_acid
Yea it does increase

OK.
I was wrong, sorry.

 

[EpicLol]

View attachment 12788

no precipitate is formed and gas formed at - electrode so it has to be sulphuric acid

 

[Lost_Life]

U

View attachment 12788

M, I DONT KNOW BUT IM SURE THAT THE LEVELS HAVE SOMETHING TO DO WITH IT

 

[thats_me]

Are you sure?
Conc.HCl , dil.HCl , both have the same pH of 1.

There was a question don remmember which ppr or which question but..
It said that there is an acid with a Ph 4 and what will be it's pH after the addition of water , the ans was pH 6

 

[EpicLol]

OK.
I was wrong, sorry.

yr still really good at chem wayyyy better than I am

 

[thats_me]

oh yeah...i got it...thanks

Ur most welcum

 

[Lost_Life]

U

B is 2,5
C is 2,8,2 which is correct

um, i mean A sorry not B :L

 

[white rose]

U
M, I DONT KNOW BUT IM SURE THAT THE LEVELS HAVE SOMETHING TO DO WITH IT

i guess u r rite...even i dont get dis ques..

 

[AAnsarii]

Are you sure?
Conc.HCl , dil.HCl , both have the same pH of 1.

dilute n conc r 4 no of molecules(in d solvent) n d acid has uniform pH as long as its not contaminated, i guess

 

[thats_me]

QUESTION !!
MJ 11 VARIANT 12..
NUMBER 3 WHY IS C NOT B :S PLEASE HELP :'(
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_ms_12.pdf

Check with a periodic table
A should be 2,1
B should be 2,5
C should be 2,8,2
D should be 2,8,8
so C is correct

 

[Lost_Life]

Check with a periodic table
A should be 2,1
B should be 2,5
C should be 2,8,2
D should be 2,8,8
so C is correct

oh

 

[EpicLol]

View attachment 12788

sry I was wrong

Look there is loads of hydrogen produced and since H2SO4 releases the most Hydrogen when electrolysed that is the answer

Cu SO4
H OH
There is only 1 H compared to S or O

Na Cl
H OH
There is only 1 H compared to the other which is either O or CL

H SO4
H OH
Notice there are 2 H's compared to the other gas which is 1 S
and we can see that the cathode has twice the more gas than the anode

I hope this helps and I hope I am not making a really stupid mistake

 

[AAnsarii]

w04, q 21
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w04_qp_1.pdf
also, qn31
help plz

 

[Student of the year]

View attachment 12788

it cannot be A bcz theres no metal formed
not B bcz the gases formed are not equal in amount (i.e H,CL are not the products)
its C bcz the -ve gas is half that of the +ve one(i.e O2 is half of H2)
(sorry , but have no idea abt D )but it could be that no solid is formed (i.e no carbon)
hope u got it

 

[EpicLol]

w04, q 21
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w04_qp_1.pdf
help plz

C
as when anything containing a nitrate ion is heated with sodium hydroxide and aluminium powder/foil , it forms ammonia gas which turns red litmus blue

 

[Maz]

w04, q 21
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w04_qp_1.pdf
help plz

Most probably it's 'C '.

 

[AAnsarii]

w04, q 21
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w04_qp_1.pdf
also, qn31
help plz

qn 31; n 32, i noe it's D but y?
q39
plz hlp

 

[Lost_Life]

View attachment 12788

im guessing that its dilute sulfuric acid because there is a HIGH CONCENTRATION OF OH- IONS HENCE DILUTE... so the level of the liquid is higher than that of the cathode (sulphate ions) while there is a LOW CONCENTRATION OF SULPHATE IONS