Chemistry: Post your doubts here!

[periyasamy]

Guys have a question here.
In the picture i post below,I dont get it all three answers given.Can anyone explain it to me.Thanks.

 

[periyasamy]

Another question here guys.Pls help.Thanks a lot.

 

[Hassan Ali Abid]

What is the meaning of ( construction lines ) ? is it the triangle ?

yes im talking about the triangle. bigger triangle must be drawn to calculate the gradient ....

 

[periyasamy]

Guys last question.Pls help.I really dont understand
For aspartic acid ,why isnt there a negative in coo ?Thank u a lot.

 

[halloffame]

Can anyone of you give me the lists of all the electrophiles and nucleophiles .

 

[1357911]

The triangle which you have drawn for calculating the gradient is too small and the marks are deducted for that.
P.s its not allowed to take those points which are in table to calculate the 'm' and you have used those points so marks will be penalized.... Am I ryt ??

nah. Not here. I did the same mistake (making a larger triangle) in my exam, and ended up taking the points which were out of the line. My marks got deducted. As long as those points are EXACTLY on the line. its correct.
Yes. It isnt allowed to take the points from the table. And for ur kind information, I havent used those points from the table.

 

[yousef]

nah. Not here. I did the same mistake (making a larger triangle) in my exam, and ended up taking the points which were out of the line. My marks got deducted. As long as those points are EXACTLY on the line. its correct.
Yes. It isnt allowed to take the points from the table. And for ur kind information, I havent used those points from the table.

does construction line mean drawing a triangle ?

 

[1357911]

does construction line mean drawing a triangle ?

yes.

 

[Hassan Ali Abid]

nah. Not here. I did the same mistake (making a larger triangle) in my exam, and ended up taking the points which were out of the line. My marks got deducted. As long as those points are EXACTLY on the line. its correct.
Yes. It isnt allowed to take the points from the table. And for ur kind information, I havent used those points from the table.

But i read in some ms or er that we should extent the lines and then a bigger triangle must be drawn to calculate the gradient ...
and just see ...u have drawn the triangle using those two particular points which means that gradient is calculated from those two points.....And is your ans the same as in ms ???

 

[1357911]

But i read in some ms or er that we should extent the lines and then a bigger triangle must be drawn to calculate the gradient ...
and just see ...u have drawn the triangle using those two particular points which means that gradient is calculated from those two points.....And is your ans the same as in ms ???

That is.. for when the points are ON the line. I couldnt find any further points ON the line which would give me a bigger triangle.
Those 2 particular points are exactly ON the line. and Yes. the gradient is correct. I checked it.

 

[Hassan Ali Abid]

That is.. for when the points are ON the line. I couldnt find any further points ON the line which would give me a bigger triangle.
Those 2 particular points are exactly ON the line. and Yes. the gradient is correct. I checked it.

Its not compulsory to draw the triangle using those particular points ....any points can be considered for drawing the triangle.

 

[1357911]

Its not compulsory to draw the triangle using those particular points ....any points can be considered for drawing the triangle.

Thats the common mistake we do. *Any points* you tae should be on the line. -_-

 

[alyazfar24]

hey can anyone give me the answers to the End-of-chapter questions
of Chemistry AS and A level coursebook
by Roger Norris, Lawrie Ryan and David Acaster
From chapter 17-30

 

[Abdel Moniem]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
Question 8

 

[halloffame]

hey can anyone give me the answers to the End-of-chapter questions
of Chemistry AS and A level coursebook
by Roger Norris, Lawrie Ryan and David Acaster
From chapter 17-30

Here u go ... https://www.xtremepapers.com/commun...l-chemistry-coursebook-cd-rom-download.10901/

download the CD-ROM of chemistry AS & A level book which contains answer to all end of chapter questions .......... Hope it helped u and hit >>>> LIKE

 

[Hassan Ali Abid]

Thats the common mistake we do. *Any points* you tae should be on the line. -_-

I never said that the anomalous points will be used to calculate the gradient ...i was saying that eg ...we have drawn a line ....and there are some points (points from the table)which lies accurately on the line ...and then its not allowed to draw the triangle using those particular points bcz even if the ans gets correct even then the marks are penalized for that.

 

[ahmed abdulla]

 

[alyazfar24]

Here u go ... https://www.xtremepapers.com/commun...l-chemistry-coursebook-cd-rom-download.10901/

download the CD-ROM of chemistry AS & A level book which contains answer to all end of chapter questions .......... Hope it helped u and hit >>>> LIKE

well thanks for ur help but I only need from chapter 17-30 and in pdf format

 

[scouserlfc]

View attachment 36911

Well u need to use the least number of amino acids from the list above to get those tripeptides.
the first one which u have to use is met-ala-gly because it says in question the polypeptide has a met amino acid which has a free amino group.

Now u just have to make the chain so as to have these tripeptides forming when your chain is hydrolyzed. Also u have been told that lysine is the amino acid at end so we have.

met-ala-gly-x-x-x-x-lys
the x above are missing aminiacids if u look carefully u will come to the conclusion that the missing ones are ala-gly-arg-val
so the sequence is :

met-ala-gly-ala-gly-arg-val-lys

I know this is a weird question i got it wrong as well when i did it i thought we need to use those tripeptides to make the chain but in reality u dont need to do that. If u have trouble let me know.

 

[ritesh isuri]

help me plz with this: A solutiion A is saturated with both calcium hydroxide and calsium sulphate. both are sparingly soluble. a)pH of A is 12.3 find concentration of OH-.
b) Ksp of calsium hydroxide =4.0*10^-5, find concentration of calcium ions in A
c)Ksp of calcium sulphhate is 2.5*10^-5, find conc of sulphate ions in A.