Biology; Chemistry; Physics: Post your doubts here!

[usama321]

i accidently attatched wrong file. see now :O

 

[Saad Mughal]

branch only means when you are extending a branch from in between a carbon chain like this
View attachment 24024

What you did was just bend the last carbon bonding, which is not a branch

That's what I said. Branched structure means that the carbon atoms are not bonded side by side, instead one of the chains goes upwards/downwards which makes it 'branched'.

 

[usama321]

That's what I said. Branched structure means that the carbon atoms are not bonded side by side, instead one of the chains goes upwards/downwards which makes it 'branched'.

when the first or the last carbon are either bended upwards or downwards, it is the same as making them straight and is not called branched. Branched is when one of the carbon atoms is turned upwards from in between that chain, not from the extreme ends, i can assure you of that.

 

[usama321]

Check this out..

actually there is only one isomer of propene, and it is a strange one, and i don't think it is included in our syllabus. This is not an isomer, as it is just like making the whole thing backwards. I was wrong about moving the double bond.

 

[nidz]

Reflux is like recollection, it is used in distillation (or when boiling liquids), the vapors of the liquid are condensed and returned to the solution (this is called reflux), it prevents loss of any liquid from the container.

It's a condition for esterfication and oxidation of ethanol, right? :/

 

[nidz]

actually there is only one isomer of propene, and it is a strange one, and i don't think it is included in our syllabus. This is not an isomer, as it is just like making the whole thing backwards. I was wrong about moving the double bond.

I agree with you. They both are not isomers, only a different way of making propene. And who knows which one CIE prefers :/
Wouldnt it be better to write the formula like this : CH3 CH=CH2 like they have shown in one of the marking scheme instead of drawing the whole structure?

 

[nidz]

Test for iodide ion.What is the meaning of the red underlined line???

It means that you should write the whole "DILUTE NITRIC ACID" instead of writing 'acidified' which actually means the same thing

 

[usama321]

I agree with you. They both are not isomers, only a different way of making propene. And who knows which one CIE prefers :/
Wouldnt it be better to write the formula like this : CH3 CH=CH2 like they have shown in one of the marking scheme instead of drawing the whole structure?

when they say draw, i think we should draw. And what is the harm in drawing, it hardly takes one minute. better safe than sorry

 

[Saad Mughal]

It's a condition for esterfication and oxidation of ethanol, right? :/

Yes. Since it is very volatile.

 

[Saad Mughal]

when the first or the last carbon are either bended upwards or downwards, it is the same as making them straight and is not called branched. Branched is when one of the carbon atoms is turned upwards from in between that chain, not from the extreme ends, i can assure you of that.

Propene has 3 carbon atoms so it can't be branched from the middle. Well, I'll look at this matter and comment on it tomorrow. I think I am wrong. Apologies for the confusion.

 

[usama321]

Propene has 3 carbon atoms so it can't be branched from the middle. Well, I'll look at this matter and comment on it tomorrow. I think I am wrong. Apologies for the confusion.

yup, that is why it has this isomer only, i searched on google.

https://www.google.com.pk/search?q=...avogadro.co.uk%2Forganic%2Fisomer.htm;325;152

and do confirm it from your teacher too.

 

[Saad Mughal]

yup, that is why it has this isomer only, i searched on google.

https://www.google.com.pk/search?q=propene isomer&safe=off&source=lnms&tbm=isch&sa=X&ei=PcN6UfXWIImSrgfY_YHIDQ&ved=0CAcQ_AUoAQ&biw=990&bih=582#imgrc=t08wyINkPxg6-M:;8CSIcRo7KR5KcM;http%3A%2F%2Fwww.avogadro.co.uk%2Forganic%2Fc3h6.gif;http%3A%2F%2Fwww.avogadro.co.uk%2Forganic%2Fisomer.htm;325;152

and do confirm it from your teacher too.

I don't have a Chemistry teacher that can answer that.

 

[usama321]

 

[thementor]

This is what your graph should look like.
View attachment 24019

however they have drawn a straight line in the marking scheme for the section you have shown in red............a straight line with a negative gradient, not even slightly curved...

 

[tdk]

Could anybody plz post the Nov 2012 QP and Mark Schemes of Physics, Chemistry and Biology.

 

[falcon678]

dudes itz available here on XP!

 

[HDIWAN]

how we should prepare for different experiments in physics paper?? theory paper?

 

[robinhoodmustafa]

Could anybody plz post the Nov 2012 QP and Mark Schemes of Physics, Chemistry and Biology.

https://www.xtremepapers.com/commun...emes-grade-thresholds-examiner-reports.22842/

 

[fatima0000]

any body please explain me cathode ray oscilloscope ??
im worried nd cant get through it

 

[fatima0000]

how a low density cloud of hydrogen in space becomes a star??