Chemistry: Post your doubts here!

[The Sarcastic Retard]

http://gopapers.net/alevel.html?_9701_w11_qp_12__9701_w11_ms_12
Q39 .. what do they mean by acidification??

Hydrolysis in 2 and 3
1 cant be.

 

[The Sarcastic Retard]

http://gopapers.net/alevel.html?_9701_w11_qp_12__9701_w11_ms_12
Q13 ... won't the SO2 oxidise to form SO3 ??

CH3SH + 3O2 ----> CO2 + SO2 + 2H2O

 

[awesomaholic101]

CH3SH + 3O2 ----> CO2 + SO2 + 2H2O

so i should know this ... thanks

Hydrolysis in 2 and 3
1 cant be.

ok

 

[awesomaholic101]

heyy!
can someone explain this please
Alkane X has molecular formula C4H10. X reacts with Cl 2(g) in the presence of sunlight to produce only two different monochloroalkanes, C4H9Cl. Both of these monochloroalkanes produce the same alkene Y, and no other organic products, when they are treated with hot ethanolic KOH. What is produced when Y is treated with hot concentrated acidified KMnO4?
A CO2 and CH3CH2CO2H
B CO2 and CH3COCH3
C HCO2H and CH3COCH3
D CH3CO2H only
The answer is B, why not A?

The chloroalkenes formed will have 2 methyl branches, only then alkenes formed by both isomers will be same.

 

[The Sarcastic Retard]

heyy!
can someone explain this please
Alkane X has molecular formula C4H10. X reacts with Cl 2(g) in the presence of sunlight to produce only two different monochloroalkanes, C4H9Cl. Both of these monochloroalkanes produce the same alkene Y, and no other organic products, when they are treated with hot ethanolic KOH. What is produced when Y is treated with hot concentrated acidified KMnO4?
A CO2 and CH3CH2CO2H
B CO2 and CH3COCH3
C HCO2H and CH3COCH3
D CH3CO2H only
The answer is B, why not A?

THere are two posiblities of forming alkenes in primary Halogenoalkane.
There is only one posiblity of forming alkene in tertiary.
Hence:

 

[Sinzzzz]

thanks alot

 

[donewithtime80]

please explain why P is MgO... isn't MgO supposed to be soluble and ionic compounds conduct in aqueous sol..?

 

[ahmed butt]

Q28?
http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w03_qp_1.pdf
http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w03_ms_1+2+3+4+5+6.pdf

 

[awesomaholic101]

View attachment 57505

please explain why P is MgO... isn't MgO supposed to be soluble and ionic compounds conduct in aqueous sol..?

I am not sure about that one too ... but MgO only dissolves slightly in water and apparently, SiO2 mp/bp is lower than that of MgO given

 

[The Sarcastic Retard]

Q28?
http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w03_qp_1.pdf
http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w03_ms_1+2+3+4+5+6.pdf

It will replace H of OH only.
H2O ; D2O
H2O ---> H+ + OH-
D2O ---> D+ + DH-

 

[donewithtime80]

https://www.xtremepapers.com/commun...9702-discussion-here.42450/page-7#post-942645

Can u please explain your working? It's going over my head

 

[The Sarcastic Retard]

Can u please explain your working? It's going over my head

I used trial and error.
I tried option A, didnt satisfied the answer, but B did. Sth like this;
Initial moles of 2P : 2
IM of 2Q and R : 0
Equilibrium moles of R : x
EM of 2Q is x/2 (1:2 ratio)
EM of 2P is 2 - x/2 (1:2 ratio and IM was 2 so we will subtrct x/2)
So addition of EM = 2 - x/2 + x/2 + x = 2 + x

 

[donewithtime80]

I used trial and error.
I tried option A, didnt satisfied the answer, but B did. Sth like this;
Initial moles of 2P : 2
IM of 2Q and R : 0
Equilibrium moles of R : x
EM of 2Q is x/2 (1:2 ratio)
EM of 2P is 2 - x/2 (1:2 ratio and IM was 2 so we will subtrct x/2)
So addition of EM = 2 - x/2 + x/2 + x = 2 + x

kayy!! thanks bro!

 

[donewithtime80]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s15_qp_12.pdf

the following questions please...

2,9,11,19,20,21,26,29,37

 

[donewithtime80]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_12.pdf

q:17 ... why can't i just cross multiply the number of moles for M? and then use n=mass/Mr to find Mr?
why does it give a different answer?

 

[SadiaMaryam]

any tips to remember the organic reactions? anyone plz! ..I often mix them up

 

[awesomaholic101]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_12.pdf

q:17 ... why can't i just cross multiply the number of moles for M? and then use n=mass/Mr to find Mr?
why does it give a different answer?

View attachment 57506

sorry didnt get u

 

[saturn21]

Ans is A..can someone explain this to me

 

[awesomaholic101]

any tips to remember the organic reactions? anyone plz! ..I often mix them up

i have replied to you on the other thread .. well, above all, ask Allah to help you remember and stay confident, you will do well iA.
ALL THE BEST PEOPLE! (Y)

 

[awesomaholic101]

View attachment 57508

Ans is A..can someone explain this to me

The concentration increases with time. At first, it rapidly increases as there are more reactant molecules so more frequent collisions and then it slows down, gradually stopping as reactants decrease and is eventually used up.