Problem Solving Strategies

@blue have you found that video

Anonymous

No. But I can tell you the solution. It's easy

Anonymous

2:24 AM

Anonymous

Which part are you having a problem with?

Anonymous

@Koolman

B

Anonymous

Remember that electric field lines from outer charge $q_2$ will end on the outer surface only

Anonymous

@Koolman Okay, I'm solving

2:27 AM

because they get cancelled inside the shell

Anonymous

Option (B) is correct

Anonymous

@Koolman

how

Anonymous

Net force on q1 is due to outer surface charge + due to q2

how can we find force by separte induced chatges inside and outside

@blue why not by inner induce charge

Anonymous

2:33 AM

@Koolman Inside surface will have no induced charge due to q2

Anonymous

The field lines will end on the surface only

Anonymous

It's like a Faraday's cage

@blue there would be inside induced charge by q1

and why not by q2

q2 induces outside surface

Anonymous

@Koolman There will also be outside induced charges due to q1. So the induced charges due to q1 will exert no force

to conserve charge it automatically induce charge in inside surface

Anonymous

2:35 AM

@Koolman No, due to q2, the induced charges rearrange on the surface itself

@blue outside charge by q1 is uniformly distributed while inside charge are non unifirmly distributed

Anonymous

@Koolman "outside charge by q2 is uniformly distributed". No, it's not.

@blue which induce charge . do you mean by q1

@blue sorry ,q1

Anonymous

@Koolman I mean by q2 only

Anonymous

@Koolman Even due to q1 the charge distribution won't be uniform as it is not in the centre

Anonymous

2:38 AM

But there is an equal and opposite induced charge due to q1 on the inner and outer surfaces so they will cancel out

outside charge by q2 is not uniformly distributed but there is uniforly distributed inner induce charge by q2

Anonymous

@Koolman There will be no inner charge due to $q_2$

Anonymous

Look at the picture ^

Anonymous

The situation is similar

2:39 AM

@blue I agree they are equal and opposite but the distribution is different

Anonymous

@Koolman That's not possible. Every finite element on the shell has to remain neutral due to induced charges by q1. That's possible only when the non-uniform distribution is cancelled out by either surfaces

@blue ohh there are both positive and negative charge nduce on outer surface by q2

Anonymous

@Koolman Right!

@blue net charge on shell is zero . But distribution of positive and negative charge is different . Am I correct ?

Anonymous

@Koolman Yes

Anonymous

2:46 AM

On the outer surface the charge is always uniformly distributed

Anonymous

@blue, I get option D, but how option B? isn't q1 hidden from q2?

I mean no line of q2 enters the shell

So how q2 exerts a force on q1

@blue due to q1 it is uniformly distributed but due to q2 it will not

Anonymous

@Koolman Right

Anonymous

@samjoe Read our previous discussion, I explained this point

2:49 AM

so net charge on outer and inner surface are not uniformly distributed

@blue

Anonymous

@Koolman Yeah, correct

Now electric field inside the shell is zero by outer induce charge + inner induce charge + q2

Anonymous

@Koolman Exactly!

we have to find dorce due to outer surface = -(q2 + inner surface)

in this how to find the force by inner surface

Anonymous

Force due to inner surface charge + force due to outer surface charge due to q1=0

Anonymous

2:55 AM

Think of when q1 is alone and q2 is superposed on this

okay I agree

Revision Questions:

1) Why is sodium fusion extract boiled with conc. HNO3 before you carry out silver nitrate test?

Anonymous

@Yashas To oxidize and remove the other stuffs like S,N and so on

2) Compare dipole moments: CH2=CH2 and CH3 - CH=CH2

@blue I got it

thanks

2:59 AM

3) Explain why 3* carbocations are more stable than 1* carbocations

Anonymous

@Yashas Second one is obviously greater

@blue Yes

@blue Reason?

@Yashas second has more

Anonymous

@Yashas Meh =P wth

Anonymous

@Yashas Inductive effect and H effect

2:59 AM

@Yashas hyperconjugation

@blue Inductive effect is negligible

2. CH3 - CH=CH2 one has higher
3. Inductive effect of Me

Anonymous

+H

@Koolman Hyperconjugation is the dominant effect.

yeah

3:00 AM

@samjoe Hyperconjugation is more dominant in both 2) and 3)

Anonymous

Which is more soluble in water Na+ ion or NH4+ ion ? :D

Hyperconjugation can cause polarity in C-H bond

@blue Na+ is smaller?

So it has higher solvation enthalpy

Anonymous

@Yashas Here's sizes won't matter as such

but Na+ exists in a lattice

NH4+ usually does not

In 2, theres unsymmetry

hydration!

Anonymous

3:02 AM

@Yashas Ugh, in solution they are free ions!

@blue I was thinking about adding a salt to the solution to get the ions

Anonymous

You're missing something important

Anonymous

NH4+ has H bond

OH

wait

Anonymous

Na+ has ion dipole interactions

3:02 AM

NH4+ -_-

how?!

hydrogen bonds

Q: Does the ammonium ion hydrogen bond with water?

2

What about oxonium ions, such as hydronium ion? Do these hydrogen bond with water? If we see hydrogen bonding as a purely electrostatic phenomenon, then why not? Ammonium ion still has nitrogen bearing a partial negative charge. Of course it can interact with positively polarized hydrogens in a...

Anonymous

@Yashas It forms hydrogen bond with water

:O

Anonymous

N is electronegative

Anonymous

And belongs to second period

Anonymous

3:05 AM

O is EN too

Anonymous

So O-H bond is polar

Yea

Only N,O and F can form hydrogen bonds

Anonymous

So H....O----H type bonds will exist

I am checking if H has significant partial positive charge in ammonium ion

the + charge is with the nitrogen

What about high hydration enthalpy of Na+ ??

3:07 AM

there are 4 hydrogens from which the nitrogen pulls electrons towards itself equally

Anonymous

@Yashas O is more EN than N

The nitrogen has to create enough partial positive charge on the H.

R-NH-R + NaNO2 + aq.H2O ----> ???

R3N + NaNO2 + aq.H2O ----->

RNH2 + CS2 ------> (P) + HgCl2 + heat ------> (Q) + (R)

R has a vermillion

1) What is Q?

2) What is R?

3) What is P?

4) What does Q smell like?

5) What is the reaction called?

6) Do 2* and 3* amines answer this test?

7) If not, why?

1 + 1 + 1 + 1 + 1 + 1 + 2 = 8 marks

*R has a vermillion color

RNH2 + PhSO2Cl + Pyridine ---> (P) + base ---> soluble in base

RNHR + PhSO2Cl + Pyridine ---> (Q) + base ---> insoluble in base

R3N + PhSO2Cl + Pryidine ----> No reaction

1) WHat is P?

2) What is Q?

3) Why is Q not soluble in base?

4) What is the reagent PhSO2Cl called?

wth , I hate these type of questions

RNO2 + Zn-NH4Cl + heat ----> (P) + Tollen's Reagent ----> Ag precipitate

1) What is (P)?

2) What is the reaction called?

3) What is the colour of the Ag precipitate?

HINT: All 3 sets of questions are from POC (Practical Organic Chemistry)

HINT2: All 3 sets of reactions are some sort of test for something.

Anonymous

3:27 AM

Hmm, I need to revise the Hoffman mustard oil reaction

Anonymous

The others I can do

give the answers :P

revise and give the answers

when you write, you'll remember better :P

Anonymous

Okay, I'll revise amines on Thursday probably :P

Anonymous

Today I'll complete hydrocarbons

Anonymous

Tomorrow alkyl halides and alcohols

3:29 AM

ok

I'll write the answers then

Anonymous

Organic is too huge man :P

@Koolman Want to try?

@Yashas Sorry , I am too weak in this . I need to revise them all

I never able to remember all these things

Anonymous

@Yashas Mustard oil

:D

Anonymous

3:32 AM

@Yashas 2 degree does

Anonymous

3 degree does not

Anonymous

3 degree doesn't have spare H :P

2 degree does not

2 degree itself does not have a spare H

N can make 3 bonds

one goes to the alkyl group

one is for the carbamic acid group

one for H

for 2 degree, two are taken for alkyl groups

so you have none left for H

Anonymous

@Yashas It does. It reacts with CS2 to form dithiocarbamic acids, but does not react with HgCl2

@blue Oh, you meant that. It is correct :P

Anonymous

3:34 AM

@Yashas This is toh boring NCERT crap which I'll revise

Anonymous

That extra H stuff which will be taken up by NaOH

You want me to put the answers or you want to give answers to all later?

Anonymous

You can put the answers, but I'll answer them again myself

4

My sir's notes

I am going to print it out

that picture has everything!

3:37 AM

actually It is in pdf form

Anonymous

@Yashas hydroxyl amine probably

@blue yes

@Koolman The examples in the diazo test are freaking me out.

Anonymous

@Yashas Hydroxyl amine reacts with Tollen? :O

Anonymous

I forgot

Anonymous

Does it? how?

3:38 AM

You just need an acid

TR is basic

They are not called oximes :c

hydroxyl amines :p

Anonymous

What's the product with hydroxyl amine + tollen?

Anonymous

OH- takes out H and then?

books.google.co.in/…

Anonymous

@Yashas Superstar the POC notes by koolman! I'll need it to revise!

looks like NEET is screwed up again this year :D

KANNUR, KERALA: A woman medical aspirant from Kerala appearing for the National Eligibility and Entrance Test at the state's Kannur centre on Sunday was shocked when she was asked by officials to remove her innerwear before sitting for the exam. Another candidate, who was wearing a pair of jeans, was asked to remove a pocket as well as metal buttons from it. No, it wasn't an act of perversion, but a "way to ensure no cheating" in the exam.
Angry candidates appearing for the test for admission to undergraduate medical courses in government and private medical colleges in the country reported…

Spoiling their mood just before the test

"The ordeal is over but it's debatable how many female candidates would have been able to write the exam properly after they were subjected to so much humiliation. I will write to Chief Minister Pinarayi Vijayan to seek action against those responsible," said state Mahila Congress President Bindhu Krishna.

rip

Anonymous

3:47 AM

wtf

Nobody can write a test after being subjected to such [insert word]

Anonymous

In WBJEE they took away my whole pencil box and threw it away :/

o0

threw it away?

Anonymous

@Yashas Yeah

Go complain!

pgportal.gov.in

Anonymous

3:49 AM

@Yashas To whom? As if they will listen

They'll listen

because the central govt does the work for you

they send notice to the concerned authority

and the concerned authority cannot ignore it

Anonymous

But WBJEE is under state gov toh

does not matter

Anonymous

Okay, I'll see. Let this JEE be over and then

NIOS and CBSE were ignoring all requests for JEE ranks and board marks to be corrected

After using the government's redressal system, they called me in two days :D

After a month, NIOS sent a letter about how the govt notice was handled.

I couldn't even register for JoSAA :/

Anonymous

3:53 AM

@Yashas Eh! That's bad

All the NIOS students in Karnataka state got only half of the practical exam marks.

and JEE was using board percentile

I got 46 marks more after the corrections were made

my initial rank was 19k :D

after the correction, it came down significantly

well, even a 0.01 percentile change can make a whole lot of change in ranks

Anonymous

@Yashas Only half ? :O phew!

Anonymous

Such nonsense

60 marks data entry practical

30 marks gone

20 marks physics, chem practical

another 20 marks gone

Anonymous

Yeah :/

Anonymous

3:57 AM

On the other hand in our ISC boards everyone in our school got over 90 percent marks. Something's fishy it seems :P Some of the students didn't even score 50 percent in the annuals

CBSE gave a lot of bonus marks last year

Anonymous

Maybe the paper checkers corrected the paper blindly :P

NIOS students never get bonus marks ,-,

unless the question was wrong

Anonymous

@Yashas How far have you completed organic?

haven't really started revision

doing GOC and POC

Anonymous

4:01 AM

I just completed GOC

Anonymous

And will complete hydrocarbons today

Anonymous

1/3 rd of qualitative analysis done

Anonymous

My maths has fortunately improved a bit

4:17 AM

CuSO4.H2O is anhydrous copper sulphate? o0

or only CuSO4

check Koolman's picture

Anonymous

@Yashas It's monohydrate....which is also colorless

Anonymous

4:33 AM

@Yashas Are you able to complete your JEE mocks in time?

Anonymous

I am being able to solve only around 60-70 percent of the previous years maths papers in time

Anonymous

And similar in physics and chem

Anonymous

I have this bad habit of spending too much time on one question

@blue nope

Anonymous

7:42 AM

Demjanov rearrangement

The Demjanov rearrangement is the chemical reaction of primary amines with nitrous acid to give rearranged alcohols.[1][2][3] It involves substitution by a hydroxyl group with a possible ring expansion. It is named after the Russian chemist Nikolai Jakovlevich Demjanov (Dem'anov, Demianov) (1861–1938). [4] == Reaction mechanism == The reaction process begins with diazotization of the amine by nitrous acid. The diazonium group is a good leaving group, forming nitrogen gas when displaced from the organic structure. This displacement can occur via a rearrangement (path A), in which one of the sigma...

Anonymous

@Yashas Carbon Suboxide + (XS) HCl ====> Product ?

7:59 AM

That isn't in the syllabus, right? o0

Anonymous

@Yashas Mechanism!

Anonymous

It's GOC man!

wot?

Anonymous

The concepts needed to solve this question are very much in syllabus

Anonymous

Just addition of H+ and tautomerization

Anonymous

8:00 AM

That's all

I had never heard of that name

but that rearrangement is just a silly one

which happens to have a name

Anonymous

@Yashas Which name?

Demjanov

Anonymous

@Yashas That's not related to this question

I was talking about that rearrangement

C3O2 :o

I had forgotten

9:05 AM

Q. pH of blood is maintained by balance between H2CO3 and HCO3-. If CO2 is increased in blood, what will happen to pH?

I think pH will reduce as CO2 is acidic, but answer given is pH does not change!!

pH decreases slightly

@samjoe The answer is ambiguous.

The blood is a buffer solution. It resists any change in pH.

However, when you add an acidic or basic component, the pH does change a little.

It does not change significantly as the buffer solution tries to reduce the change.

But if we use henderson equation, pH does change, ya same as you said!

But there will always be some tiny change.

Yea, that question is bad.

Hmm many errors in my revision package..

Where did you get it from?

9:09 AM

from my coaching institute, i don't have other good source atm..

Solve old JEE papers

Which book do you use to practice organic?

JEE papers?

Thats a good idea!

Anonymous

JEE papers are the best

Anonymous

For revision

9:53 AM

why there would be second reaction

BaSO4 is a poison

you get cis alkene from the first reaction

In first reaction alkane will be formed

the second reaction gives you the alkane

no

first reaction won't give you alkane

Hydrogenation happens on the surface of the catalyst Pd

BaSO4 is a powder

It covers the surface

with that reagent we cannot do partial reduction

and this reduces the efficiency of the catalyst

alkynes have a higher tendency to be reduced than alkenes

so the alkynes will form alkenes

Anonymous

9:55 AM

First is cis alkene

it does undergoes partial reduction

Anonymous

Then syn addition of D2

Can we get partial reduction product from first reaction

Anonymous

@search BaSO4/CaCO3/NickelBoride and H2 cause partial reduction to alkenes

Anonymous

They cannot adsorb alkenes on their surface

Anonymous

9:58 AM

Partial reduction "to" alkenes

so which reagent cannot cause partial reduction

Anonymous

@search Just Pt/Pd H2 will cause complete reduction