Chemistry: Post your doubts here!

[A star]

http://maxpapers.com/syllabus-materials/chemistry-9701-a-level/attachment/9701_w13_qp_5/
9701_w13_qp_5 | Max Papers

is ka 9701/53/O/N/13
ka Q3 ka graph check karo kaesae banae ga?

 

[A star]

asd syed1995 daredevil and all othersssss

 

[Muskan Achhpilia]

Q5 - A is correct. Iodine is I2, a molecule, hence it has covalents bonds between the atoms. It also has van der Waals forces of attraction between I2 molecules.

Q33 - Anything from Period 1 to Period 2 cannot have an expansion of the octet. Nitrogen is in Period 2 and so cannot expand its octect, whereas Phosphorus can. This is because Phosphorous d orbitals can also be used in bonding since there isn´t a big enough of an energy gap, whereas Nitrogen´s d orbital are far away and so a lot of energy is needed for the electrons to occupy them, which doesn´t favour Nitrogen.

Q37 - Ammonium ion is NH4+. If you count the electrons properly (4 for the hydrogens, 1 less because it has formed a positive ion and 7 for nitrogen) you should get 10 electrons. Because NH4+ has bonds to 4 things and has no lone pairs, the bonds are spaced out tetrahedrally (since its the most energetically stable geometry for 4 bonded things and no lone pairs). Tetrahedral arrangements have bond angles of 109.5 degrees.

Hope it helps.

Thanks

 

[Muskan Achhpilia]

I also have these questions as doubts-



Thank you!!!

 

[sidbloom1995]

Thanks. I think i'll be able to do 29. And for 24, how do we know it's a Nucleophilic Reaction?

nucleophile is a group with lone pairs of electrons and OH- is a nucleophile!
we also know that during this reaction the OH will displace the Br from bromoehtane so it will most likely be by the SN (nucleophilic substitution), and as the name suggest, in this one nucleophile displaces the other so we know that both are nucleophile!

 

[ahmed abdulla]

Went through my chem paper 4 and had this doubts .. Any help ?
3 e (iv )
5 b (iv )
7 c (iv )
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_43.pdf

 

[sidbloom1995]

I also have these questions as doubts-
View attachment 38412 View attachment 38413 View attachment 38414 View attachment 38415


Thank you!!!

Q3. we add the first and second ionisation energies of Al: 1820 + 577 = 2397 kJ/mol
now we add the the ionisation energies of each element given and the one that add up to 2397 will be our answer!
so when we add the 1st and 2nd ionisation energy of Co we get: 1640 + 757 = 2397 kJ/mol so our ans is A

Q4. in this one we have to find the one that DOES NOT HAVE 126 NEUTRONS!
they have give us the total nucleon number so when looking at the periodic table, only take the proton number of the element!
Bi = 209 - 83 = 126
Pb = 208 - 82 = 126
Po = 210 - 84 = 126
Tl = 208 - 81 = 127
so D= T l will be our ans as it does not have the magic no. 126 nucleon!

Q7. im not sure about this one but i do know that since Phosphorus is in group 5 it will form bonding like ammonia and will have the bond angle of 107
since they havent given us 107 in our answer we have to chose and answer close to 107! so logically speacking 109 is closer to 107 but wa cant have that as the answer! out angle should be smaller them or equal to 107 so the next closest no. is 104, thus the answer 104!

Q18. again im not sure of this answer so please confirm this one with someone else!
hydrogen bond will be present! so our ans will narrow down to C and D!
since NH3 is basic it ionises the water and thus we will have ions in the solution!
thus our answer is D

 

[mehria]

what's hybridization?? (related with AS-chemistry Syllabus)

 

[daredevil]

Question explaination needed :-/

I didnt get how they calculated it

 

[daredevil]

what's hybridization?? (related with AS-chemistry Syllabus)

splitting up of orbitals ... so that they are at the same energy level.

 

[A star]

what's hybridization?? (related with AS-chemistry Syllabus)

merging of orbitals of different energy level to form orbitals of same energy level inorder to for single covalent bonds

 

[mehria]

splitting up of orbitals ... so that they are at the same energy level.

i knw ... but wat's the difference between sp, sp2, sp3 hybridisations??

 

[Muskan Achhpilia]

Q3. we add the first and second ionisation energies of Al: 1820 + 577 = 2397 kJ/mol
now we add the the ionisation energies of each element given and the one that add up to 2397 will be our answer!
so when we add the 1st and 2nd ionisation energy of Co we get: 1640 + 757 = 2397 kJ/mol so our ans is A

Q4. in this one we have to find the one that DOES NOT HAVE 126 NEUTRONS!
they have give us the total nucleon number so when looking at the periodic table, only take the proton number of the element!
Bi = 209 - 83 = 126
Pb = 208 - 82 = 126
Po = 210 - 84 = 126
Tl = 208 - 81 = 127
so D= T l will be our ans as it does not have the magic no. 126 nucleon!

Q7. im not sure about this one but i do know that since Phosphorus is in group 5 it will form bonding like ammonia and will have the bond angle of 107
since they havent given us 107 in our answer we have to chose and answer close to 107! so logically speacking 109 is closer to 107 but wa cant have that as the answer! out angle should be smaller them or equal to 107 so the next closest no. is 104, thus the answer 104!

Q18. again im not sure of this answer so please confirm this one with someone else!
hydrogen bond will be present! so our ans will narrow down to C and D!
since NH3 is basic it ionises the water and thus we will have ions in the solution!
thus our answer is D

Thank you!!

 

[daredevil]

i knw ... but wat's the difference between sp, sp2, sp3 hybridisations??

sp means s orbital + 1 p orbital

sp2 means s orbital + 2 p orbitals

sp3 means s orbital + 3 p orbitals

the p orbitals that are not hybridized make bonds on their own at their normal energy level...

 

[ahmed abdulla]

Question explaination needed :-/

I didnt get how they calculated it

Quoted from examiner report :

" The data needed a careful analysis,
since the orders were not obvious at first glance. Taking the first and last rows in the table, and
comparing the rates to the concentrations of the complex, it could be seen that as [complex]
doubles, so does the rate. Thus they are proportional to each other, and so the order with respect
to [complex] is one. This could be confirmed by comparing rows one and two. The fact that (CO)
seems to have no effect on the rate indicates that the order with respect to (CO) is zero. "

let me now if you didnt understand

 

[daredevil]

Quoted from examiner report :

" The data needed a careful analysis,
since the orders were not obvious at first glance. Taking the first and last rows in the table, and
comparing the rates to the concentrations of the complex, it could be seen that as [complex]
doubles, so does the rate. Thus they are proportional to each other, and so the order with respect
to [complex] is one. This could be confirmed by comparing rows one and two. The fact that (CO)
seems to have no effect on the rate indicates that the order with respect to (CO) is zero. "

let me now if you didnt understand

how do we know that [CO] has no effect on rate?

 

[ahmed abdulla]

how do we know that [CO] has no effect on rate?

When ratio of Conc : rate are Equal eg 1:1 l 2:2 >> its first order with the taken reagent
When ratio of Conc : rate are 2:1 ie ( conc has higher ratio > its Zero order with the taken reagent
When ratio of Conc : rate are 1:2 ie ( conc has lowerratio > its Second order

 

[mehria]

sp means s orbital + 1 p orbital

sp2 means s orbital + 2 p orbitals

sp3 means s orbital + 3 p orbitals

the p orbitals that are not hybridized make bonds on their own at their normal energy level...

but how r we supposed to knw that wat type of hybridisation is present in a specific molecule ??

 

[ahmed abdulla]

how do we know that [CO] has no effect on rate?

Seems you didnt get it !
take Exp 1&2 ... divide the two concentraions eg exp2 by exp1 .. you get 2.11 .. divide rates.of . exp2 by exp1 > you get 1.45
conc. is not in proportion with rate , and rate DECREASES so its zero order
thats what i remember my teacher told me!

 

[ahmed abdulla]

Can someone have a look at my doubts ??