Chemistry: Post your doubts here!

[PhyZac]

Wallaikum As Salam !
Its quite simple actually !
it tells u first that the fertilizer has 30% P2O5 content so it means actually u have 100g of fertilizer of which 30g is P2O5
so just find the mass of phosphorus content using simple ratio ,
142(Mr of P2O5) ----- 30
62 ------ x
x=13.1%

there is a big jump in iE values from 3 to 4 abt 2000 KJ but this isnt really enuf to tell us that the new shell starts here probably it shows the start of s subshell so now u can be assured that its from grp 5 now remember how hydrogen bonds with nitrogen and requires exactly 1 electron like Cl atoms and has a formula NH3 so Cl will have NCl3 (the use of atoms here is just for an example its not necessary its the real one )

Jazak Allah Khairan,,,,Thank you so much! May Allah reward you for your help to all students..Ameen I understood it now

 

[PhyZac]

Asslamu Alikum Wa Rahmatullah Wa bRakatoho
27 What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and
(CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium
Sorry....But can anyone explain why C...?

 

[N.M]

Asslamu Alikum Wa Rahmatullah Wa bRakatoho
27 What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and
(CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium
Sorry....But can anyone explain why C...?

WaAlaikum us Salam wr wb

I think it is C b/c the rxn of alcohols with halogen atom is a type of nucleophilic reaction(Sn reaction)
There are two types of Sn reactions Sn1 and Sn2
(CH3)3CCH2OH will react by Sn1 mechanism
And (CH3)2CHCH2CH2OH will react by Sn2 mechanism.

 

[PhyZac]

WaAlaikum us Salam wr wb

I think it is C b/c the rxn of alcohols with halogen atom is a type of nucleophilic reaction(Sn reaction)
There are two types of Sn reactions Sn1 and Sn2
(CH3)3CCH2OH will react by Sn1 mechanism
And (CH3)2CHCH2CH2OH will react by Sn2 mechanism.

Jaak Allah Khairan....Thank You So much....!!!!!!!!!!!!! May Allah reward for the help...Ameeeen!

 

[magnesium]

WHAT is the functional group in haloalkane? REPLY PLZZ!!!!!!!!!!!

 

[nightrider1993]

WHAT is the functional group in haloalkane? REPLY PLZZ!!!!!!!!!!!

The halogen is the functional group.

 

[Adil Bhatti]

please can anyone help me with topic wise pastpapers of chemistry p2 and p4???? please send me the link which really works... thanks in advance

 

[scouserlfc]

please can anyone help me with topic wise pastpapers of chemistry p2 and p4???? please send me the link which really works... thanks in advance

I dont think there is any link for topical papers present online

 

[izzahzainab]

In the upper atmosphere chlorofluoroalkanes (CFCs) are broken down to give chlorine radicals
but not fluorine radicals.
What is the best explanation for this?
A Fluorine is more electronegative than chlorine.
B Fluorine radicals are less stable than chlorine radicals.
C The C–F bond is stronger than the C–Cl bond.
D The chlorine atom is larger than the fluorine atom

C. Because the C-Cl bond is much weaker than C-F bond, it is easily broken and chlorine free radicals are released.

 

[chris123]

Hi,

Do u have alll the past papers for 2012(June and Nov) chemistry? I can't find some 2012 on this site.
Also I need further maths (all modules including mechanics) and Maths and physics.

Thanks

Thanks

 

[usman138]

I am switching from Fsc. to A levels and i have decided to take A levels privately through Cambridge.Anyone please reply me with the answers of the following:
1)From which books can i prepare the `advanced practical skills` paper for chemistry?Is there any practical book for A levels as in case of Fsc.
2)On the registration form,there are two choices for practical paper of chemistry(33: Advanced practical Skills 33
34: Advanced practical Skills 34).What is the difference b/w these two options?Which shud i prefer?
3)On the registration form,one option in the maths section says`64: Carried Forward June 2012 AS 1+4
Mark`what does this 1+4 mean?
Thanks.

 

[scouserlfc]

Hi,

Do u have alll the past papers for 2012(June and Nov) chemistry? I can't find some 2012 on this site.
Also I need further maths (all modules including mechanics) and Maths and physics.

Thanks

Thanks

For June 2012 all resources are present for Nov 12 they may not be there so go here !
http://www.xtremepapers.com/community/threads/october-november-2012-cie-question-papers.22842/

 

[magnesium]

are aldehyes soluble in water. y?

 

[magnesium]

WHAT is the difference between hydration and hydrolysis? PLZ REPLY!!!!!!!!!!!!!!!!

 

[magnesium]

'Alkenes react with HX (hydrogen halides) in COLD at room temperature'. one of my friends read this statement in a text book.
IS'NT this statement contradictory.?????????????? PLZ REPLY!!!!!

 

[magnesium]

What is the alkyl group in this haloalkane
CH2Br2BrCH??????????????

 

[Nut with Gut]

hello
can anybody post the notes of just A2 chemistry ?? i had some notes but they were mixed so i want just A2 ones

 

[Warrior66]

Asalam-o-Alaikum!
could someone answer this question for me and tell me HOW to do it..please, asap??
When 1 mol of N2O4 gas is allowed to come to equilibrium with NO2 gas under standard conditions, only 20% of the N2O4 is converted to NO2.
N2O4 <> 2NO2 Hr = + 58 kJmol-1
Calculate the value of Kc for this reaction. Assume that the volume of the reaction mixture is 1 dm3.

 

[TERMINATOR]

Salam.can some1 plz help me solve this mcq

 

[Warrior66]

Salam.can some1 plz help me solve this mcq

Wa Alaykum Asalam Warahmatullahi Wabarakatuhu!
when i tried the question out i got B: 0.05 moldm-3 which i think you got too...but see here we have to read the question very carefully (this was a question already asked by someone and answered by another someone so that's how i understood)
it says "in the ratio of 15 g : 30 g : 15 g" NOT "in the ratio of 15 : 30 :15" Note: There IS a difference!
therefore:
Ans : A
- the percentage of N is the fertiliser is 15/100 = 0.15%
- in 14g of fertiliser, the amount of N is 14 x 0.15 = 2.1g
- the number of moles of N is 2.1g of N is 2.1/14 = 0.15 mole
- concentration = mole/volume, hence, 0.15/5 = 0.03moldm-3
(Jazak' Allahu Khairan to that person!)