Chemistry: Post your doubts here!

[TheDealer]

Q19?
http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w07_qp_1.pdf

 

[Amy Bloom]

Can somebody confirm if I'm right:
1 (a) What is the electronic configuration of a nickel atom?
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d8

(b) Predict the electronic configuration of a nickel (II) ion.
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d6

 

[Anonymous']

Can somebody confirm if I'm right:
1 (a) What is the electronic configuration of a nickel atom?
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d8

(b) Predict the electronic configuration of a nickel (II) ion.
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Yes, that's correct.. heheh..

 

[TheDealer]

Can somebody confirm if I'm right:
1 (a) What is the electronic configuration of a nickel atom?
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d8

(b) Predict the electronic configuration of a nickel (II) ion.
My answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Well the configuration for nickel atom is right...but for the nickel ion is wrong. The 2 electrons are removed from 4s as 4s has lower ionisation energy than 3d.
For ion, the e.c. should be : 1s2 2s2 2p6 3s2 3p6 3d8

 

[TheDealer]

Anonymous...i think u need to recheck that. I'm sure the e.c. for the nickel ion is wrong.

 

[Anonymous']

Anonymous...i think u need to recheck that. I'm sure the e.c. for the nickel ion is wrong.

Oh yeah! my bad, hehe.. yes yes, you're right, sorry.. I totally forgot about that.. heheh..

 

[TheDealer]

What is the product when (CH3)3CCH2OH is reduced by conc. sulphuric acid?

 

[smzimran]

What is the product when (CH3)3CCH2OH is reduced by conc. sulphuric acid?

No reaction...

 

[Asad]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s11_qp_11.pdf
MCQ 2
how is it A. Shoudnt it b D?

 

[TheDealer]

Answer should be A because oxidation number decreases from 5-3 , 3-2 , 2-1 , 1-0
So biggest decrease is in A...from NO3- to NO2-

 

[TheDealer]

oh btw... in NO3- , N will have oxidation state of +5, because overall oxidation state of molecule should be -1.
+5-6 = -1
Same will be the case for NO2-

 

[Asad]

THANK YOU
please explain mcq 9 0f same paper

 

[Amy Bloom]

Oh yeah! my bad, hehe.. yes yes, you're right, sorry.. I totally forgot about that.. heheh..

Thank you all.
But I'm still doubtful whether 3d is found slightly above 4s. Even if this is so, 3d, 3p & 3s are found in quantum level n=3. That is why i removed electrons from 3d first (farther from the nucleus, so lower ionisation energy.) I'm I right?

 

[TheDealer]

well thats actually wrong...3d is closer to the nucleus than 4s...though it defies logic
But i guess at the end of the day, we all just have to remember that 3d is closer to nucleus than 4s. Since 4s is outermost in Nickel, shielding (screening) effect of inner electrons means that they will have least attraction to nucleus. N thats why they'll be removed first.
Crazy ain't it?

 

[omg]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w09_qp_42.pdf
can any1 explain me q8. part c(ii) and d??

 

[smzimran]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w09_qp_42.pdf
can any1 explain me q8. part c(ii) and d??

8(c)(ii)
M peak is due to Cl-35 and Cl-35
M+2 peak is due to Cl-35 and Cl-37
M+4 peak is due to Cl-37 and Cl-37...

 

[Amy Bloom]

well thats actually wrong...3d is closer to the nucleus than 4s...though it defies logic
But i guess at the end of the day, we all just have to remember that 3d is closer to nucleus than 4s. Since 4s is outermost in Nickel, shielding (screening) effect of inner electrons means that they will have least attraction to nucleus. N thats why they'll be removed first.
Crazy ain't it?

Yeah indeed!. Thank you!!

 

[omg]

8(c)(ii)
M peak is due to Cl-35 and Cl-35
M+2 peak is due to Cl-35 and Cl-37
M+4 peak is due to Cl-37 and Cl-37...

and part d???

 

[Amy Bloom]

What is the product when (CH3)3CCH2OH is reduced by conc. sulphuric acid?

Normally the alcohol cannot be reduced into an alkane in one step because the -OH bond is reinforced by the 3 electron repelling methyl groups, so not easily removed.
So, no reaction.

 

[Amy Bloom]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s11_qp_11.pdf
MCQ 2
how is it A. Shoudnt it b D?

Let the oxidation number of N be x
For:
NO3- .............A............... NO2- .............B...........NO .............C...............N2O................D........ N2
x - 6 = -1 ......................... x - 4 = -1 ..................... x - 2 = 0 .................... 2x - 2 = 0 .................... 0
x = +5 ................................ x = +3 ........................ x = +2 ........................ x = 1 ...........................0
|___ Change = 2________| |__change =1____| |___change=1___| |___change=1___|

Since a change is seen only in A, the answer is A. The change in D is 1, so is in B and C. Hence D is wrong.

P.S Sorry I had to put dots coz when i post, the writings compact & mix up. Hope you'll understand. If you're confused, i'll post it as an image. ok?