Chemistry: Post your doubts here!

[Soldier313]

Aoa wr wb

I need some detailed explanation on how to do qn 3 c of this paper pleasee

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_42.pdf
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_ms_42.pdf

JazakAllah khair

 

[iKhaled]

Aoa wr wb

I need some detailed explanation on how to do qn 3 c of this paper pleasee

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_42.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_ms_42.pdf

JazakAllah khair

i use a faster way of doing this question other than lookin at the potential values of the electrodes..use the reactivity series u learnt in ur igcse and any element below hydrogen in it is the one that will be reduced at the cathode and any element above the hydrogen then hydrogen ions from the water will reduce instead forming H2 for the anions learn this

SO4^2- , CO3^2- , NO3^- , F^- , OH^- , Cl^- , Br^- , I^-1

the ease of oxidation of the anion is easier going from left to right. any anion before OH will stay and OH^- from water will oxidize to oxygen instead and any element after the OH will oxidize instead of the OH in water. beware of chloride ions, because this ion depends on its concentration. if it is concentrated it will oxidise to chlorine gas and if it is in dilute then oxygen will oxidize instead

did u get it ?

 

[hela]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

MAINLY PROPERTIES OF OXIDES AND CHLORIDES

 

[Soldier313]

i use a faster way of doing this question other than lookin at the potential values of the electrodes..use the reactivity series u learnt in ur igcse and any element below hydrogen in it is the one that will be reduced at the cathode and any element above the hydrogen then hydrogen ions from the water will reduce instead forming H2 for the anions learn this

SO4^2- , CO3^2- , NO3^- , F^- , OH^- , Cl^- , Br^- , I^-1

the ease of oxidation of the anion is easier going from left to right. any anion before OH will stay and OH^- from water will oxidize to oxygen instead and any element after the OH will oxidize instead of the OH in water. beware of chloride ions, because this ion depends on its concentration. if it is concentrated it will oxidise to chlorine gas and if it is in dilute then oxygen will oxidize instead

did u get it ?

Oh okay, thanx a lot.

But er, i am quite familiar doing it with the electrode potential method. The problem arose when i could use that method for all the answers except the one where we had to decide if fluorine or oxygen gas is given off in electrolysis of AgF :/ Perhaps you can elaborate on that bit with reference to potential values?

Thanx a ton for your help.
May Allah (SWT) bless you!

 

[hela]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

MAINLY PROPERTIES OF OXIDES AND CHLORIDES OF PERIOD 3

 

[hela]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

MAINLY PROPERTIES OF OXIDES AND CHLORIDES OF PERIOD 3 PH

 

[strangerss]

alright see do uk the formula v1p1 = v2p2 ( we took that in IG physics)

before we connect the flasks we have 2(1) + 2(1) = v2p2 ( v2p2 are the values of the volume and pressure of gasses after connecting the flasks) when we connect the flasks the volume (v2) will be 1+2 =3

so 2(1)+2(1) = 3p2
p2 = 4/3 therefore the answer is A..did u get it ?

Wow mashallah I wouldn't how figured it out after a billion years XD , this question is very tricky , what if some one never took physics! hehe. any ways thanks a lot for the help

 

[Manobilly]

InshAllah

 

[Manobilly]

InshAllah

 

[Student12]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

How much information i know is that:
Gp 2 with Water:

Be has no reaction with Water cuz it forms a BeO layer.
Mg + H2O --> Mg + H2 (no rxn with cold water)
Ca + 2H2O --> Ca(OH)2 +H2 Same with Sr & Ba
Sr and Barium react vigorously with cold water, forms a soluble hydroxide.

 

[iKhaled]

Oh okay, thanx a lot.

But er, i am quite familiar doing it with the electrode potential method. The problem arose when i could use that method for all the answers except the one where we had to decide if fluorine or oxygen gas is given off in electrolysis of AgF :/ Perhaps you can elaborate on that bit with reference to potential values?

Thanx a ton for your help.
May Allah (SWT) bless you!

u wanna know how to use the potential values to find the answer for AgF ?

 

[iKhaled]

Wow mashallah I wouldn't how figured it out after a billion years XD , this question is very tricky , what if some one never took physics! hehe. any ways thanks a lot for the help

no problem!

 

[Soldier313]

u wanna know how to use the potential values to find the answer for AgF ?

yes please, because when i did it, i got such an answer that F2 rather than O2 would be given off, while the ms says O2 is given off. :/
Thanx.

 

[Manobilly]

InshAllah

 

[Alice123]

no problem happy to help just pray for me that i get stright As .
well the reaction is dehydration hence it contains a alcohol and carboxylix acid and the alcohol is dehydrated to a double bond with this structure
CH2=CH-CO2H hope u get it

dint see da question properly before....Thanks....May Allah bless u with the best grades!!!!

 

[iKhaled]

yes please, because when i did it, i got such an answer that F2 rather than O2 would be given off, while the ms says O2 is given off. :/
Thanx.

ok see...

O2/OH^- = 0.4V and F/F^- = 2.87 so OH ion is easier to be oxidized than F^- so O2 will form at the anode..got it ? BUT i don't know why the mark scheme gives a wrong answer to this method with Br not SO4 but for the cations it gives all the answers right..do u solve it that way too?

 

[PANDA-]

How much information i know is that:
Gp 2 with Water:

Be has no reaction with Water cuz it forms a BeO layer.
Mg + H2O --> Mg + H2 (no rxn with cold water)
Ca + 2H2O --> Ca(OH)2 +H2 Same with Sr & Ba
Sr and Barium react vigorously with cold water, forms a soluble hydroxide.

Are you sure? I thought that
Mg + 2 H2O(l) --> Mg(OH)2 + H2 (slow)
Mg + H2O(g) --> MgO + H2 (fast)

 

[syed1995]

Are you sure? I thought that
Mg + 2 H2O(l) --> Mg(OH)2 + H2 (slow)
Mg + H2O(g) --> MgO + H2 (fast)

That's correct. But Mg only very slightly hydrolyzes.. so if one writes no reaction or very slow reaction he should get the mark.

 

[knowitall10]

from which book have u snapped this

From the older version of the orange one.. right now, we have the orange one right?
yeah, the book that was endorsed by Cambridge two years ago. umm.. wait, i'll post a pic.

 

[knowitall10]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

Don't you use your Chemistry text book? It's pretty clear there; to get rid of the confusion, write the formulas down and make tables the way you would remember. I know, i really hate periodicity and the group 2 and 7 chapter! Whatever happened to the phrase: "The brain is like a sponge".
:/