Chemistry: Post your doubts here!

[Rizwan Javed]

It's called 'fac' 'mer' isomerism. Because around the metal, the 6 ligands form an octahedron which can go in 3 different different directions so form 2 different isomers.
First you need to understand that there are 3 directions and really imagine them in your head this way, when you look at the complex.
Simple line --- plane of the paper
wedges --------bonds towards the viewer
dashed --------bonds away from the viewer

In the mer isomer, the three similar ligands define a meridian of the octahedron. Meridian is like the imaginary circle that runs north to south (like on the earth's surface, from the North Pole to the South Pole). So in the 'mer' isomer, we start, for instance, in the plane of paper, then the 2nd similar ligand is towards you, then the 3rd similar is again in the plane of paper. Imagine going through that, you will find you just made the 'mer' of octahedron.
View attachment 62140
Like in the image, the isomer labelled mer has Cl ligands in 2 different directions (in plane of the paper and going away from you)
Similarly, in mer isomer, the ligand H2O goes in 2 different directions.

In the 'fac' isomer, the similar ligands define the face of octahedron, which will run in 3 different directions. Like in the image, you can see one Cl ligand goes in the plane of paper, one out, towards you and the 3rd in (away from you). This makes the face of isomer.
To draw the two isomers, just draw the 'fac' isomer first, by making 3 directions and putting each same type of ligand in different direction. Then to make 'mer', just alternate one type of ligand in one direction with the other type in another direction. Like over here, you just alternate The H2O in plane of the paper with the direction towards you, which makes the H2O go in just 2 directions instead of 3 and do similarly with Cl.
There's a lot of imagination of directions required here so even if you can't do that, just remember 'fac' will have each type of ligand in 3 directions while 'mer' will have each type of ligand in 2 directions.

Wow! AMAZING! That cleared so many doubts!

 

[darks]

Hey if someone could clear one or more of these syllabus points for me, it would be really helpful...

-21.3. b)Explain the significance of hydrogen bonding in pairing of bases in DNA in relation to replication of genetic information.

-e) Discuss how polymers have been designed to act as:
i)non solvent based adhesives e.g epoxy resins and superglues
ii)conducting polymers e.g polyacetylene

-Also how much do we need to know about biodegradability of polymers?

- I was unable to find drawn diagrams of primary/secondary/tertiary structures of protein in any marking scheme... If someone could provide me with the 3 diagrams with the bonding shown as we have to draw them in exam.. it would be great

-electrophoresis diagram as shown in marking scheme (a 3d diagram) is really tough to draw... can we draw a 2D one.. with everything labelled?

sorry, i know this is a lot to ask on the last day these were the only topics left where i am having issues. Even if you could clear one of these points, that would be great

 

[HELLNO]

hahahah that's okay
post yours too

Its okay lol, you explanation was clear enough

 

[areeba240]

9701/w16/41
qtn 5 (c)(i) how to find the relative peak area
(d)(i)
need explanation for these two parts....

 

[areeba240]

9701/w13/43
qtn 6(f)
plzz explain

 

[darks]

Hey if someone could clear one or more of these syllabus points for me, it would be really helpful...
-how much do we need to know about biodegradability of polymers?
- I was unable to find drawn diagrams of primary/secondary/tertiary structures of protein in any marking scheme... If someone could provide me with the 3 diagrams with the bonding shown as we have to draw them in exam.. it would be great
-electrophoresis diagram as shown in marking scheme (a 3d diagram) is really tough to draw... can we draw a 2D one.. with everything labelled?

Edited the quote above^^
Discussed few points with friends so those are clear. Only these remain! Please help!! thanks!!

 

[HELLNO]

Edited the quote above^^
Discussed few points with friends so those are clear. Only these remain! Please help!! thanks!!

>Biodegradable polymers are the ones that can get hydrolysed when an acid is added to them, you don’t have to know much, just know if any bond that can be hydrolysed in the polymer then its biodegradable, also know the advantages of biodegradable polymers over non-biodegradable ones
-Biodegradable plastics take less time to break down
-Renewable
-Good for the environment (no environmental harm)
-Require less energy to produce
-Easier to recycle
-Non-toxic
Thats it…

>Hmm primary structure is basically just the basic sequence of amino acids in a polypeptide

Secondary is the alpha helix and beta pleated sheets (I have never seen a question where they asked to draw this though)

And tertiary is the 3D structure including the 3 bonding (Hydrogen, disulphide and ionic interactions)

>Yes its okay, as long as everything is clear, and is fully labelled they will give you the marks

Tell me if you don't get any of the above^^

 

[HELLNO]

Edited the quote above^^
Discussed few points with friends so those are clear. Only these remain! Please help!! thanks!!

Whoops I don't know why the pictures aren't appearing!
Can you see anything? And how do I make them appear

 

[darks]

>Biodegradable polymers are the ones that can get hydrolysed when an acid is added to them, you don’t have to know much, just know if any bond that can be hydrolysed in the polymer then its biodegradable, also know the advantages of biodegradable polymers over non-biodegradable ones
-Biodegradable plastics take less time to break down
-Renewable
-Good for the environment (no environmental harm)
-Require less energy to produce
-Easier to recycle
-Non-toxic
Thats it…

>Hmm primary structure is basically just the basic sequence of amino acids in a polypeptide

Secondary is the alpha helix and beta pleated sheets (I have never seen a question where they asked to draw this though)

And tertiary is the 3D structure including the 3 bonding (Hydrogen, disulphide and ionic interactions)

>Yes its okay, as long as everything is clear, and is fully labelled they will give you the marks

Tell me if you don't get any of the above^^

You're a life saver thanks a lot!
the images are not visible.. try lowering the size maybe? you can do that through paint.. then resize.
The question came in s08 p4... Q8

 

[HELLNO]

You're a life saver thanks a lot!
the images are not visible.. try lowering the size maybe? you can do that through paint.. then resize.
The question came in s08 p4... Q8

Haha! Glad to know! and anytime
And oh really, I will check that out

Its not working :s

Well basically the primary one is just the aminoacid with the amide link (covalent bond) joining them
Secondary the a helix is coiled with hydrogen bonds holding the structure, Beta is the same, but less extensive hydrogen bonds
Tertiary is the 3 bondings I mentioned above.
Type on google images and you can see how do we draw the disulphide, hydrogen and ionic interaction...

 

[darks]

Haha! Glad to know! and anytime
And oh really, I will check that out

Its not working :s

Well basically the primary one is just the aminoacid with the amide link (covalent bond) joining them
Secondary the a helix is coiled with hydrogen bonds holding the structure, Beta is the same, but less extensive hydrogen bonds
Tertiary is the 3 bondings I mentioned above.
Type on google images and you can see how do we draw the disulphide, hydrogen and ionic interaction...

Thanks! got it! Good Luck!

 

[sara_queen]

In w16 p41
q5 part c)1 how do we find the relative peak area

 

[Saad the Paki]

For the reaction conditions of diazotisation, should we write the temperature as a range as in ms like " Temp <10° C " or do we write a specific temperature like " Reaction should be carried out at 5°C" ?

 

[Saad the Paki]

In w16 p41
q5 part c)1 how do we find the relative peak area

The relative peak area in NMR is the number of H atoms represented by that peak

 

[HELLNO]

For the reaction conditions of diazotisation, should we write the temperature as a range as in ms like " Temp <10° C " or do we write a specific temperature like " Reaction should be carried out at 5°C" ?

<10 degrees
Thats what the syllabus says

 

[Zaki ali asghar]

In China, the concentration of blood glucose, C6H12O6, is measured in mmol / l . In Pakistan, the concentration of blood glucose is measured in mg/ dl. The unit l is a litre (1dm3 ). The unit dl is a decilitre (0.1dm3 ). A blood glucose concentration of 18.5mmol/l indicates a health problem. What is 18.5mmol/l converted to mg/ dl?
A 33.3mg/ dl B 178mg/ dl C 333mg/ dl D 3330mg/ dl can someone solve this?

 

[anastasia grey113]

In China, the concentration of blood glucose, C6H12O6, is measured in mmol / l . In Pakistan, the concentration of blood glucose is measured in mg/ dl. The unit l is a litre (1dm3 ). The unit dl is a decilitre (0.1dm3 ). A blood glucose concentration of 18.5mmol/l indicates a health problem. What is 18.5mmol/l converted to mg/ dl?
A 33.3mg/ dl B 178mg/ dl C 333mg/ dl D 3330mg/ dl can someone solve this?

where is this from?

 

[anastasia grey113]

i was doing this practical in which KMnO4 was also being used as a test for salt analysis
y is that done?

 

[hammadfbh]

Chemistry Paper 33 May June 2017, anybody knows what is coming?

 

[JamesV Gibbs]

Once you have this paste, stir in some orange zest. Apply the mask to your face and allow it to set for 15 minutes.