Chemistry paper 42 may/june 11

[mrpaudel]

actually..i think, for the electrode question...mukesh is correct......We jus have to look at the E* values...and write the products....so there shud b Ag F2 Mg SO2 Fe Br2...these are the products...!

 

[beacon_of_light]

i don't exactly remember but yes, the gaseous 'atoms' Not 'ions' were being in a reaction to make a solid, so that wasn't supposed to be lattice one, so i wrote formation which might be a - or a + value

I am sure that is an acid-base reaction since HF donates a proton and NH3 accepts a proton

CAn we write exothermic reaction there???

Well I don't think so since they were asking "type" of a reaction and exo or endo do not come under them!

 

[beacon_of_light]

actually..i think, for the electrode question...mukesh is correct......We jus have to look at the E* values...and write the products....so there shud b Ag F2 Mg SO2 Fe Br2...these are the products...!

I don't think so...Look concentrations matter a lot and normally in As when we didn't know about E* values, we used to look at the reactivity series...the one lower in the series reduces quickly and I used this concept to solve the question...

 

[bionology]

I don't think so...Look concentrations matter a lot and normally in As when we didn't know about E* values, we used to look at the reactivity series...the one lower in the series reduces quickly and I used this concept to solve the question...

I second you here, I think this concept was to be applied.

P.S, my no was abrupt, not "rude". We are here to discuss the paper, "discuss" here means both the correct and the wrong things, I got some of my stuff wrong too, doesn't means someone here was trying to "show me attitude" or was "proving me wrong", hope the guy who misunderstood me, got it clear now....Lets get back to the topic now

 

[zeebujha]

@XENON
yes it does... When we extract DNA. only small amount of DNA we got. ( STR ). that's why we are using PCR first. then we cut by the restriction enzyme. It was on my mind.

This thing is debatable I guess. If we amplified the whole of the DNA sample, you would be amplifying the unnecessary fragments as well. If we then obtained restriction fragments using restriction enzymes, the extraction would be a headache I guess. I think it would be better, as the application booklet suggests, to obtain the required restriction fragment first and then amplify it.

The booklet states:
" For PCR, after the DNA has been broken up into pieces in the usual way, an individual segment is extracted." This is then amplified. I think this makes perfect sense.

 

[zeebujha]

@beacon. Yes it is but it supposed to be OH in the terminal end. OHCH(C2H5)COOH.
1. Extract dna
2. Using PCR
3. Restriciton enzyme
4. Put in agragose gel
5. Carry out electrophoresis
6. Forgot. Lol.

Doesn't restriction enzyme come before PCR?

No PCR comes b4 restriction...PCR increases DNA amount and then cut into fragments by restriction enzymes!

One problem of PCR is having a pure enough sample of DNA to start with. Any unnecessary fragment will also will also be amplified if we carried out PCR first. By the way, can't we increase the amount of DNA after we have obtained the required fragment?

 

[samy]

actually..i think, for the electrode question...mukesh is correct......We jus have to look at the E* values...and write the products....so there shud b Ag F2 Mg SO2 Fe Br2...these are the products...!

i also think he is rite..coz i myself also just looked at the E values and my answers are similar to these..!!

 

[zeebujha]

okay guys, lemme try to give a ridiculous explanation. Suppose E value is how accurately you can kick a ball into the goal post. Concentration is how many people there are who want to kick the ball. If there are many people to kick to the ball, despite your highest accuracy in kicking the ball, you are never going to touch the ball on the first place let alone score a goal. Scoring a goal is akin to being oxidised and the number of people used to determine the relative concentration. In aqueous solution, the number of people who want to kick the ball is large. So, the ion with the largest E value will never get to oxidise as their already are many candidates in far greater number who want to get oxidised (in this case OH-). So, it is OH- that will kick the ball simply because there are many of them, the Br- never even gets to touch the ball , let alone score the goal!!!!!!!!! So, relative concentration is equally important too!
I would be surprised if the explanation made any sense, lol. :lol: