Chemistry: Post your doubts here!

[Liv2Stdy]

Assalamu Alaikum Warahmathulahi Wabarakathuhu

Can any one please explain me this Question................

The Answer is B....
Im pretty sure that the answer wont be Either C or D but i just have a doubt like why wouldn't it be A .. Confused... Please Help!!!!!!!1
Thanks in Advance

Here's why it'll never be either of those answers

 

[Liv2Stdy]

Hey guys! i have a doubt in 9701_s04_qp_2 question (3)(c)(iii) please help! Thanks in advance
View attachment 50680
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s04_qp_2.pdf

Ok so if you wrote the equation, you'd see that according to stoichiometry, 2 moles of NH3 is required to react with 1 mole of H2SO4. From this, you can get the no of moles of H2SO4

No of moles of H2SO4 required = 1/2 x 0.05(Found in the earlier part!) = 0.025 moles.

Now just apply to C = n/V

C= n/V

V = n/C

V = 0.025/0.5 x 1000 (I multiplied it by 1000 to convert it into cm^3)
V = 50 cm^3

OK?

 

[Farhad221]

Asslamoalikum,
I have some problems with the following questions can someone help me as soon as possible. Thanks in advance

 

[Farhad221]

can someone explain me this question
What is the electronic configuration of an element with a second ionisation energy higher than that of each of its neighbours in the Periodic Table?
A 1s2 2s2 2p6 3s2
B 1s2 2s2 2p6 3s2 3p1
C 1s2 2s2 2p6 3s2 3p2
D 1s2 2s2 2p6 3s2 3p3

OK so the answer is B and the reason is the element must be from group 3
The second electron removed will be from sub-shell s which is nearer to the nucleus than p sub-shell. Hence its ionisation energy is higher than group 4 s and higher than group 2 s because it has a higher atomic number.

 

[Al. Ahmad]

can anyone help me with this please?

 

[manya]

Asslamoalikum,
I have some problems with the following questions can someone help me as soon as possible. Thanks in advanceView attachment 50731 View attachment 50731 View attachment 50731 View attachment 50732 View attachment 50731 View attachment 50732 View attachment 50733 View attachment 50731 View attachment 50731 View attachment 50731

sulphuric acid is an oxidising agent. it is powerful enough to oxidise HBr to Br2 and HI to I2, but it cant oxidise HF and HCl

H2SO4 +HBr= Br2 +2H2O+SO2
H2SO4+HI=I2+2H2O+SO2

 

[manya]

y must it belong from Group 3 because all atoms do not have 3 electrons in there outer shells. it must belong to period 3

 

[manya]

Asslamoalikum,
I have some problems with the following questions can someone help me as soon as possible. Thanks in advanceView attachment 50731 View attachment 50731 View attachment 50731 View attachment 50732 View attachment 50731 View attachment 50732 View attachment 50733 View attachment 50731 View attachment 50731 View attachment 50731

question regarding reduction of chromium, the answer is D because in Cr2O3, u have to do +6/2 for the oxidation no. of chromium

 

[manya]

Asslamoalikum,
I have some problems with the following questions can someone help me as soon as possible. Thanks in advanceView attachment 50731 View attachment 50731 View attachment 50731 View attachment 50732 View attachment 50731 View attachment 50732 View attachment 50733 View attachment 50731 View attachment 50731 View attachment 50731

for identification of P, Q and R, SiO2 will not conduct in a liquid state so it can not be P

 

[princess Anu]

why do period 3 group 2 metals not show variable oxidation states but sulphur , phosphorus do?

 

[princess Anu]

why is A the right answer?
why would C decolourise AQueous BRomine?
Haven't we learnt that only alkene ( out of all the homologous series) decolourises aq bromine and it is a universal test for alkene as well:/

 

[shazmina]

Here's why it'll never be either of those answers

View attachment 50730

Thanks alot sis May God bless u immensely

 

[princess Anu]

can somebody do this?

answer is E

 

[Liv2Stdy]

Thanks alot sis May God bless u immensely

You're welcome !

 

[Bba321]

Hi please tell me why have we used the equation Fe 3+ + e -----> Fe 2+ in this question and not the equation of fe3+ given in data booklet?
Thanks

 

[Abdel Moniem]

Hi, how can I prepare for my chemistry A-level exams? Iam currently revising the chapters of the book. I am worried because I haven't yet started solving past papers.

 

[Hassan Ali Abid]

Hi, how can I prepare for my chemistry A-level exams? Iam currently revising the chapters of the book. I am worried because I haven't yet started solving past papers.

AS level or A2 ? Without making any delays , start solving the past papers...Refer the mark scheme .....Keep revising the organic part cz majority of the paper is based from that part so make sure you dont lose much of the marks from those questions.
Once you're done with these ,then start practising P5.

 

[Hassan Ali Abid]

Hi please tell me why have we used the equation Fe 3+ + e -----> Fe 2+ in this question and not the equation of fe3+ given in data booklet?
Thanks
View attachment 50786

Bcz in the question its clearly given that the final colour of the solution is Blue which means , at the end we are left up with fe+2....definately then we'll use the equ in which iron +3 will reduce to iron +2 rather then using the other equ....
Hope you have got it ..ryt!

 

[Abdel Moniem]

AS level or A2 ? Without making any delays , start solving the past papers...Refer the mark scheme .....Keep revising the organic part cz majority of the paper is based from that part so make sure you dont lose much of the marks from those questions.
Once you're done with these ,then start practising P5.

I am taking both AS level and A2, my major problems are with the practical papers. I am retaking chemistry AS level this year, along with the A2. Last year I scored 2 A's in my theory papers and a U grade on my practical paper. Have you got any suggestions on how I study both P3 and P5?

 

[Abdel Moniem]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s05_qp_4.pdf\
4bii)