Chemistry: Post your doubts here!

[Hinafatima]

 

[Hinafatima]

Need help for this question please ?

 

[Bhargav Poudel]

Hinafatima Answer is B. 0.1 mole of Propanol uses 9/20 mole of 02. 12dm3 is 0.5 mole, so 0.05 is unused. The 0.45 mole of used O2 gives a certain mole of CO2, which you can convert into dm3 and add the dm3 of 0.05 unused mole of O2.

 

[Hinafatima]

Hinafatima Answer is B. 0.1 mole of Propanol uses 9/20 mole of 02. 12dm3 is 0.5 mole, so 0.05 is unused. The 0.45 mole of used O2 gives a certain mole of CO2, which you can convert into dm3 and add the dm3 of 0.05 unused mole of O2.

How come 9/20 mole?? can you please expalin?

 

[Hinafatima]

How come 9/20 mole?? can you please expalin?

Oh , ok I have got the answer, thank you so very much for the help you extended

 

[DeadlYxDemon]

Need Help1 How to do this? I really have no Idea!

 

[DeadlYxDemon]

Need Help! How to do this? I really have no Idea!

 

[Areeb Mohsin]

Does anybody know how to calculate Equilibrium Moles in a Kc question
Pls tell me as soon as you can
its URGENT

 

[Mayisha M]

Does anybody know how to calculate Equilibrium Moles in a Kc question
Pls tell me as soon as you can
its URGENT

The formula for Kc is Kc = ([H+][anion])/[acid]
I'm not entirely sure what kind of math you're stuck in but if you post the question, I might try to solve it for you.

 

[DangerXJeff]

Hey guys! i have a doubt in 9701_s04_qp_2 question (3)(c)(iii) please help! Thanks in advance

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s04_qp_2.pdf

 

[shazmina]

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

 

[The Sarcastic Retard]

Doubt. Whole b part. Ty.

 

[manya]

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

 

[Charlotte20102013]

Can someone help me with this question please

Calculate the pH of a mixture of 25cm3 of 0.1M Ca(OH)2 and 20cm3 of 0.1M HCl.
I was given the answer 12.82 but I'm not sure if it's the correct one.

Thank you!

 

[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