Chemistry MCQ thread...

[Zishi]

explanation

C, as usual, by eliminating all options. And because carbon atom gets a +ve charge, so it gets electron deficient - so we may call it an electrophile.

 

[xHazeMx]

explanation

The intermediate is a carbocation. It has a positive charge so it's capable of accepting a lone pair of electrons.
It's an electrophile.

i got the same answer but just was making sure. more questions are coming soon.

 

[Zishi]

explanation

The intermediate is a carbocation. It has a positive charge so it's capable of accepting a lone pair of electrons.
It's an electrophile.

i got the same answer but just was making sure. more questions are coming soon.

Bring them on. Though I may not answer them because I'll be off to clear concepts of a friend of mine.

Why can't it be C?

We already answered and explained it. See the previous posts.

 

[Anonymousx3]

Why can't it be D?

 

[xHazeMx]

sure zishi !! .. no problem u can answer the questions after u r done. u r such a bless to xtremepapers

 

[Zishi]

Why can't it be D?

Because at very high temperature, aluminium nitrate will decompose to form aluminium oxide.

sure zishi !! .. no problem u can answer the questions after u r done. u r such a bless to xtremepapers

Ah, thanks.

 

[xHazeMx]

Why can't it be D?

Al2O3 has an oxide layer which prevents any further reaction so it's C

 

[sniper7137]

Hey. Can anyone help me with Questions 5 and 34 of May June 2007 Paper 1?

 

[Zishi]

Hey. Can anyone help me with Questions 5 and 34 of May June 2007 Paper 1?

Q5 : B
It's because we're taking hydrogen bonds between ammonia molecules to convert it into a gas.

Q34: C, i.e 2 and 3 are correct.1 is wrong, because when molten, ionic chlorides do conduct electricity.

 

[Zishi]

Hey. Can anyone help me with Questions 5 and 34 of May June 2007 Paper 1?

Q5 : B
It's because we're taking hydrogen bonds between ammonia molecules to convert it into a gas.

Q34: C, i.e 2 and 3 are correct.1 is wrong, because when molten, ionic chlorides do conduct electricity.

Oops, sorry. I guess I saw May June 006 question paper. wait for 2007

 

[Saturation]

Thanks for clearing up the previous doubt! Ok, I remember this qs was discussed before, but anyways:

http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf

Number 11. My textbook says that the rate of reaction always starts from the highest, and then as the reactants are used up and all, it decreases with time! So, in that case shouldn't the answer be D?

 

[Zishi]

Hey. Can anyone help me with Questions 5 and 34 of May June 2007 Paper 1?

For question number 5, see this: http://en.wikipedia.org/wiki/Cyanide

For question 34 D, because only 1st option gives us two(more) moles of a gas from one mole.

 

[xHazeMx]

what could be the answer and why?

 

[Zishi]

Thanks for clearing up the previous doubt! Ok, I remember this qs was discussed before, but anyways:

http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf

Number 11. My textbook says that the rate of reaction always starts from the highest, and then as the reactants are used up and all, it decreases with time! So, in that case shouldn't the answer be D?

No, because we're doing it in presence of a catalyst, so first of ALL the rate will increase. After that when concentrations of reactants become low, the rate decreases. Got it?

what could be the answer and why?

I guess 3. First tell me that Am I right?

 

[xHazeMx]

yes u r right it is B , but how?

 

[Zishi]

yes u r right it is B , but how?

Because deuterium atoms can only replace hydrogen atoms in alcohols. It's a fact, so learn it.

 

[xHazeMx]

yes u r right it is B , but how?

Because deuterium atoms can only replace hydrogen atoms in alcohols. It's a fact, so learn it.

u mean the hydrogen atoms bonded to the O atom are the number of hydrogen atoms replaced? and does it work with aldehydes, acids and esters too ?

 

[Zishi]

yes u r right it is B , but how?

Because deuterium atoms can only replace hydrogen atoms in alcohols. It's a fact, so learn it.

u mean the hydrogen atoms bonded to the O atom are the number of hydrogen atoms replaced? and does it work with aldehydes, acids and esters too ?

No, only for hydroxyl groups.

 

[sakibfaiyaz]

What exactly do they mean by NEIGHBOURS? shouldn't it in a normal way mean any atom next to it (up, down, left and right)?....In that cause B shouldn't be the answer (as Boron's second IE is greater than that of aluminium)

 

[Zishi]

What exactly do they mean by NEIGHBOURS? shouldn't it in a normal way mean any atom next to it (up, down, left and right)?....In that cause B shouldn't be the answer (as Boron's second IE is greater than that of aluminium)

All the options are neighbours to each other - that is they differ by one proton number from each other.

Sorry gotta go will answer it some time later. I don't rely on my answer, but I'd say B.