Physics, Chemistry and Biology: Post your doubts here!

[EpicLol]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w09_qp_11.pdf
why is 13 D?

chlorine goes out as it is concentrated leaving OH ions behind and H ions go away leaving the Na and the NaOH is there at the cathode which goes blue/purple as it is basic.....

 

[AAnsarii]

but Cl2 bleaches litmus paper.. is it the same for universal indicator?

sorry, it turns it scarlet, ans is D?

 

[fishcook]

acids are acidic due to the presence of H+ ions right?
and alkalines are basic because of the presence on OH- ions?

 

[AAnsarii]

chlorine goes out as it is concentrated leaving OH ions behind and H ions go away leaving the Na and the NaOH is there at the cathode which goes blue/purple as it is basic.....

y is oh at anode? cl went ryt?

 

[AAnsarii]

acids are acidic due to the presence of H+ ions right?
and alkalines are basic because of the presence on OH- ions?

yes

 

[fishcook]

chlorine goes out as it is concentrated leaving OH ions behind and H ions go away leaving the Na and the NaOH is there at the cathode which goes blue/purple as it is basic.....

but wont that form like somewhere in the middle? why does the cathode change into purple/blue.. it only contains Na+ ions which while the anode has OH- ions.. :S

 

[EpicLol]

y is oh at anode? cl went ryt?

yea CL went and its NaOH at cathode as the Na is at cathode and the OH moves towards the cathode to form NaOH which is basic.....my teacher just said metals are like nasty things who do not like to move and the OH ions float around towards these nasty things and form NaOH

 

[AAnsarii]

yea CL went and its NaOH at cathode as the Na is at cathode and the OH moves towards the cathode to form NaOH which is basic.....my teacher just said metals are like nasty things who do not like to move and the OH ions float around towards these nasty things and form NaOH

nyc way 2 xplain

 

[EpicLol]

w03http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w03_qp_1.pdf q 21, how do u noe?

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

 

[fishcook]

w03http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w03_qp_1.pdf q 21, how do u noe?

you have to learn the test for anions and cations.. no other way!

 

[EpicLol]

Does density increase or decrease as we go down group 1,2,3,4,5,6,7,8
Thx

 

[AAnsarii]

you have to learn the test for anions and cations.. no other way!

sorry, not dat qn pprhttp://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w03_qp_1.pdf q21

 

[AAnsarii]

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

sorry again, not dat ppr

 

[GetSomeLife]

w03http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w03_qp_1.pdf q 21, how do u noe?

The metal is Aluminium. Remember the test for nitrate and you'll see

 

[AAnsarii]

The metal is Aluminium. Remember the test for nitrate and you'll see

the ppr is http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w03_qp_1.pdf, sorry the earlier 1 was by mistake

 

[Lost_Life]

c, they just want 2 c dat u notice solution, so solution will only b d case where d dissolved solute(s) is/r soluble. here comes d soluble/insoluble stuff. i hp u noe what salts r soluble n the rest which arent, if u dont tell

nah, i know, but now im confused, see there was this question mj 07 , number 22
Aqueous lead(II)nitrate is added to a solution containing iodide ions.Lead(II) iodide is formed.
which type of reaction takes place?
A.Neutralisation
B.oxidation
C.percepitation
D.reduction
so is it C??

 

[FATIMAH]

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

thanks

 

[AAnsarii]

nah, i know, but now im confused, see there was this question mj 07 , number 22
Aqueous lead(II)nitrate is added to a solution containing iodide ions.Lead(II) iodide is formed.
which type of reaction takes place?
A.Neutralisation
B.oxidation
C.percepitation
D.reduction
so is it C??

yeah, ms says C

 

[GetSomeLife]

the ppr is http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w03_qp_1.pdf, sorry the earlier 1 was by mistake

The answer is D as the PH "6" (acidic) cannot be formed by adding 2 alkaline solutions to each other!

 

[AAnsarii]

The answer is D as the PH "6" (acidic) cannot be formed by adding 2 alkaline solutions to each other!

so if u want 2 verify, do u do something like average d solun's added?