Chemistry: Post your doubts here!

[_Ahmad]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_22.pdf

Can anyone please explain Q1 especially Q1 (c) i).

 

[_Ahmad]

Could you please link me to the paper, or a screenshot of the exact entire question please.

Sorry but there is no such question in the pastpapers and this is the entire question which i have.

 

[kitkat <3 :P]

(b)(ii)
one mol of diesel requires 23 mol of O2. one mol of H2O2 produce 1/2 moles of O2. so it 2*23 = 46 mol of H2O2 will be required
(c)
Mr = (15*12)+32=212
mass = 212 tonnes = 212X10^6 grams
n(diesel)=mass/mr=212X10^6 grams /212=1X10^6 mol
n(H2O2)=(46)*n(diesel)=46* 1X10^6=46X10^6 moles
Mr of H2O2=2+16+16=34
Mass of H2O2 = n(H2O2)*34=46X10^6*32=1564X10^6 grams = 1564 tonnes

Thank u

 

[Haya Ahmed]

what do we call nucleiphiles and electrophiles .. atoms or molecules or compounds or elements or substances

 

[asma tareen]

what do we call nucleiphiles and electrophiles .. atoms or molecules or compounds or elements or substances

i think they can be both ions and atoms as nucleophiles are species that can be anions or any electron defiecient atom
while electrophile can be cation :/

 

[Haya Ahmed]

i think they can be both ions and atoms as nucleophiles are species that can be anions or any electron defiecient atom
while electrophile can be cation :/

In definition what am I supposed to say !

 

[omaaaar]

In definition what am I supposed to say !

The definition given in the book is
An electrophile is an acceptor of a pair of electrons
A nucleophile is a donator of a pair of electrons

 

[AbbbbY]

Sorry but there is no such question in the pastpapers and this is the entire question which i have.

So then where did you get this question. It has insufficient detail. I believe the full question will have something to do with graphite.

 

[AbbbbY]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_22.pdf

Can anyone please explain Q1 especially Q1 (c) i).

Easy question. Been asked here quite a lot recently.

Look, moles of NaOH used = 0.045
Moles of NaOH that react with HCl = 0.005

The remaining NaOH is what reacted with the acid so acid remaining = 0.040

Equilibrium concentrations = 0.04 0.04 0.06 0.06
If you don't get the abridged explanation let me know and I'll go step by step.

BTW, anyone A2 will tell you this is an incorrect question as the NaOH will hydrolyse the ester formed but let's just assume it magically doesn't.

 

[Suchal Riaz]

what do we call nucleiphiles and electrophiles .. atoms or molecules or compounds or elements or substances

Species is the correct word

 

[MYLORD]

Which Exam paper is this ?

How to draw this :
PS : As students take care , this might be the question for you this session !!!
View attachment 41393

 

[Dexterwarrior12]

What about nmr spectroscopy in A2? Like, should I be memorising the Peaks at certain chmical shifts?

 

[Browny]

Can anyone please give me marking scheme explanations for what are electrophiles, nucleophiles and free radicals?

 

[AbbbbY]

How to draw this :
PS : As students take care , this might be the question for you this session !!!
View attachment 41393

I was practicing P4's and I just came across this. Why would it pop up in AS if it's in P4 :/

 

[robinhoodmustafa]

Can anyone please give me marking scheme explanations for what are electrophiles, nucleophiles and free radicals?

Electrophile : a particle with a positive charge to gain electrons
Nucleophile Particles with negative charge to donate electrons
Free radical are neutral atom obtain from homolytic fission

 

[robinhoodmustafa]

In definition what am I supposed to say !

Electrophile : a particle with a positive charge to gain electrons
Nucleophile Particles with negative charge to donate electrons
Free radical are neutral atom obtain from homolytic fission

 

[AbbbbY]

What about nmr spectroscopy in A2? Like, should I be memorising the Peaks at certain chmical shifts?

Lol. How exactly would that work?
The peaks vary depending on the compound and the shift depends on the environment.

 

[Haya Ahmed]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_22.pdf

What is the difference in Question 3(b) iii and Q3 (c) iii why is the answer of the enthalpy change here is positive and here is negative !! can someone help me Please!!!

 

[Mohammed salik]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_22.pdf

What is the difference in Question 3(b) iii and Q3 (c) iii why is the answer of the enthalpy change here is positive and here is negative !! can someone help me Please!!!

In first one Heat is given out so temp of surrounding Increased so Exothermic ie Negative
Second one Temp decreased , Heat absorbed so ENDOTHERMIC i.e Possitive!

 

[AbbbbY]

Okay people. Just a little confusion I've got left.
Could you guys let me know all the reagents that'd give each of 1, 2 and 3. Also, let me know if any of the 3 is not possible.

Namehere Suchal Riaz