Chemistry: Post your doubts here!

[drowning-in-studies]

hey guys how's the paper today?

idk...I guess the threshold will be high?

 

[alevel_student]

I want classified past paper for HALOGENOALKANES any idea where can i get them ?????

 

[Destinyrulex]

Hey people!
I have done chemistry in A levels. Please let me know if there are any doubts, I would be glad to help

 

[Thought blocker]

I want classified past paper for HALOGENOALKANES any idea where can i get them ?????

you can click this : https://www.xtremepapers.com/commun...αтι¢ѕ-ѕ¢αηηє∂-ρυяє-мαтн-вσσкѕ-υρℓσα∂є∂.33891/

the 4th line in pink, click it and search the chemistry thingy u need. do like my thread if i helped.

 

[wolfestein99x]

Please explain asap

 

[wolfestein99x]

Please explain asap

Dont bother i got it

 

[3abder7man]

Salam
Can anyone please explain why the answer is C, not D?

 

[wolfestein99x]

Salam
Can anyone please explain why the answer is C, not D?
View attachment 61442

Relative size , LE is direcrly proptional to the charge/ionic radi , CaS will have ggreater ionic radi (0.1*0.18) hence LE will be lesser

 

[elmansy]

Hi i want to ask why the answer is that for this question
2No2 =N2O4
40% of the moles present at equilibrium is N2O4. If the total pressure of the system is 2 atm, the numerical value of the equilibrium constant, kp is .........the answer is 0.56 why? Thanks

 

[wolfestein99x]

elmansy kp= partial pressure of products^n / partial pressure of reactants^m
partial pressure = total pressure X no.moles of / total number of moles.
pressure = 2atm
partail pressure of N2O4 = 2 X (40/100) = 0.8
partail pressure of NO2 = 2 X (60/100) = 1.2

Kp = 0.8 / (1.2)^2 = 0.56 .

read the book this was a simple question

 

[Aishayasin]

PART A TO C can anyone explain in detail

 

[Thought blocker]

View attachment 61481View attachment 61481
View attachment 61482
PART A TO C can anyone explain in detail

2)
a) As I2 is formed, the solution will turn to purple.
b) Refer this link : https://www.xtremepapers.com/community/threads/chemistry-p4-a2-only.15983/page-10#post-276332
c) Rate = change in conc/change in time. Thus draw tangent at conc of 0.001 as that s initial conc. And make a triangle to calculate gradient and that is your initial rate.

 

[madridtas_CR7]

Can anyone explain this question and solve?

 

[Thought blocker]

Q = mc(t2 - t1)
Q = 45 * 4.18 * (34.7 - 23.4)
madridtas_CR7

 

[madridtas_CR7]

Q = mc(t2 - t1)
Q = 45 * 4.18 * (34.7 - 23.4)
madridtas_CR7

http://pastpapers.papacambridge.com.../Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

 

[Thought blocker]

http://pastpapers.papacambridge.com/Cambridge International Examinations (CIE)/AS and A Level/Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

http://pastpapers.papacambridge.com/Cambridge International Examinations (CIE)/AS and A Level/Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

As it is exothermic reaction sign will be -ve.
And calculation is :
answer of 2b(i) * 10^-3 / 2(bii) = -85.02 kj/mol

 

[selrey]

Element X forms X- ions that can be oxidised to element X by acidified potassium maganate (VII). Ehat could be the values of the first four ionisation energies of X?
A) 418 3070 4600 5860
B) 577 1820 2740 11600
C) 590 1150 4940 6480
D) 1010 1840 2040 4030
Ans is D. Can someone pls explain?

 

[elmansy]

elmansy kp= partial pressure of products^n / partial pressure of reactants^m
partial pressure = total pressure X no.moles of / total number of moles.
pressure = 2atm
partail pressure of N2O4 = 2 X (40/100) = 0.8
partail pressure of NO2 = 2 X (60/100) = 1.2

Kp = 0.8 / (1.2)^2 = 0.56 .

read the book this was a simple question

Many thanks

 

[Thought blocker]

Element X forms X- ions that can be oxidised to element X by acidified potassium maganate (VII). Ehat could be the values of the first four ionisation energies of X?
A) 418 3070 4600 5860
B) 577 1820 2740 11600
C) 590 1150 4940 6480
D) 1010 1840 2040 4030
Ans is D. Can someone pls explain?

A is potasssium
B is Aluminium
C is Calcium
D is Iodine

Group VII can only form X- ions so ansewer is D

 

[nehaoscar]

Here are complete AS and A2 notes for chemistry 9701!
The notes include each and every point of the syllabus

https://www.xtremepapers.com/community/threads/9701-chemistry-notes.43471/

Please like and share if you find them helpful
Check out my signature for more A level notes and revision resources!