Chemistry: Post your doubts here!

[hassam]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_42.pdf
q3 c (i) carbon aslo has an empty 2p orbital so why it cant react

 

[miss irfan]

please somebody explain the ratio question in november 2011 paper 43 q5

 

[USMAN Sheikh]

Help needed as soon as possible plsssssss be quick in correcty reply !!! Do explain me the following questions pls 11 16 22 23 40 pls uickly JAZAKALLAH !!

 

[trgirl]

AoA,
Q7:
1 is tetrahedral so 109 degrees
2 is trigonal planar so 120 degrees [Remember that pie bons are not considered while checking bond angles!]
3 is bent / v-shaped so 105 degrees

So, smallest first, it is 3 < 1 < 2
So, C is correct!

Q8:
Hess Law:
View attachment 6991
Enthalpy change = 4(-394) + 5(-286) - (-2877) = - 129 kJ mol-1
So, the answer is B

Q10:
Kc = [CH3CO2C2H5] [H2O] / [C2H5OH] [CH3CO2H]
4 = (x)(x) / (1-x)(1-x)
4 = (x / 1 - x)^2
(x / 1 - x)^2 = 4
Taking square root
x / 1 - x = 2
x = 2 - 2x
3x = 2
x = 2/3
So, B is the answer!

​

cool explanation

 

[hmlahori]

To W07 Q9, is the answer B?
This is a redox reaction, with the sulphite oxidised to sulphate. Oxidation and reduction always come together. With sulphur oxidised, the "metal" must be reduced. You can see the change in oxidation number of sulphur is plus 2 (from +4 to +6). So if 1 mole of "metal" reacts with 1 mole of sulphite, the "metal" should experience a change of minus 2 in its oxidation number in order to compensate the oxidation. In this case, according to the volumes and molar concentrations, the mole ratio of "metal" to sulphite is 2 : 1, so the "metal" is reduced by only 1 oxidation number, so it's from +3 to +2.
W07 Q36,
1 should not be correct. The reaction must happen since sulphuric acid is acidic and potassium iodide is basic.
2 is correct since concentrated sulphuric acid is a strong oxidising agent, and iodide ion is a fairly good reducing agent, the redox reaction shall take place.
3... I cannot be sure, but that 1 is wrong and 2 is correct shall make you able to deduce that the answer is C.

Thanks can you explain the rest too?

 

[USMAN Sheikh]

PLS koi mere bhe help krod o yar

 

[hmlahori]

Can someone please give explanations to these paper 1 questions?​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

Q3 What does 'ground state' mean? And r we supposed to rite the 1s2 2s2.... electronic configuration to know the answer?​

Q21 Does an alcohol get oxidised by hot, concentrated manganate(7) ions?​

Q31 Why is the answer B not A? all the three statements seem correct.​

and Q38 Why cant the answer be B?​

 

[USMAN Sheikh]

Hm lahori can u help me pls ?

 

[Amy Bloom]

Can somebody explain this:
H-F----------------------- ▲Hf = -271 Kjmol-1
H-Cl---------------------- ▲Hf = -92 Kjmol-1
H-Br---------------------- ▲Hf= -36 Kjmol-1
H-I------------------------ ▲Hf = +26.5 Kjmol-1
Do i need to speak about the decreasing stability of the hydrides???

Explain Why's the trend in ▲H formation becoming more endothermic down Group VII????

 

[hmlahori]

Help needed as soon as possible plsssssss be quick in correcty reply !!! Do explain me the following questions pls 11 16 22 23 40 pls uickly JAZAKALLAH !!

really sorry i only have an explanation for Q16. I only solve variant 1 papers cuz thats what we will get. And variant 2 is a little harder.

Q16 Aluminium oxide is an amphoteric oxide so can act as both an acid or a base. So lets consider all the options. it cannot be A as a base does not react with a base. it cannot be C or D as the structure and bonding does not necessarily decide the dissolving of a substance. Answer has to be B as aluminium oxide will act as an acid and react with the base sodium hydroxide and dissolve in it.

 

[hassam]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_42.pdf
q3 c (i) carbon aslo has an empty 2p orbital so why it cant react

 

[Spunkyfarhan]

Hi everyone, assalamoalaikum!!

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah other people here will help me and you all.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!
Thanks!
Jazak Allah Khair!

Chemistry Notes:

Data Booklet

http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.

My Doubt is chemistry Its self

 

[hm12]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_42.pdf
q3 c (i) carbon aslo has an empty 2p orbital so why it cant react

CCl4 does not react because it does not have empty d orbitals in its valence shell which is used to except electron from oxygen of water molecule

 

[USMAN Sheikh]

PLS MERE MADAD KRDO KOI PLS
Help needed as soon as possible plsssssss be quick in correcty reply !!! Do explain me the following questions pls 11 16 22 23 40 pls uickly JAZAKALLAH !!

 

[hassam]

CCl4 does not react because it does not have empty d orbitals in its valence shell which is used to except electron from oxygen of water molecule

yar lekin 2p orbital is still vacant......so like BCl3 why cant CCl4 react...

 

[hm12]

PLS MERE MADAD KRDO KOI PLS
Help needed as soon as possible plsssssss be quick in correcty reply !!! Do explain me the following questions pls 11 16 22 23 40 pls uickly JAZAKALLAH !!

22 is C there are three reactions of alcohol which produce chloro alkane one with PCl 3 one with PCl5 and one with SOCl2 in our syllabus
40 is D i just remember studying carboxylic acid and alcohols reaction with metals in our syllabus i cant explain others because i couldn't solve them either so u need to take someone else help

 

[hm12]

yar lekin 2p orbital is still vacant......so like BCl3 why cant CCl4 react...

yar compare CCl4 with SiCl4 not with BCl3 coz BCl3 diagonally hay Si kay periodic table may so it would have properties similar to SiCl4 i dont know if u have studied about that i cant explain it more than this take someone else help if you do not get it

 

[USMAN Sheikh]

22 is C there are three reactions of alcohol which produce chloro alkane one with PCl 3 one with PCl5 and one with SOCl2 in our syllabus
40 is D i just remember studying carboxylic acid and alcohols reaction with metals in our syllabus i cant explain others because i couldn't solve them either so u need to take someone else help

FOR 22 wont it be D????

 

[USMAN Sheikh]

PLS MERE MADAD KRDO KOI PLS
Help needed as soon as possible plsssssss be quick in correcty reply !!! Do explain me the following questions pls 11 16 22 23 40 pls uickly JAZAKALLAH !! NO ONE IS ABLE TO SOLVE THEM

 

[hm12]

FOR 22 wont it be D????

no told you when SOCl2 is there no other option can be correct