This discussion is now closed.

Check out other Related discussions

AQA CHEM2 2nd June 2015 [Official thread]

Can someone explain how increasing pressure would increase the yield. Lets say the haber process and you increase the total pressure. What happens to yield and why?

Reply 341

9clpc9

2

Original post by Dr. Swiftie

I'm pretty sure the water is neither oxidised or reduced because it is a disproportionation reaction so the chlorine is reduced and oxidised

Cl2 + H2O (reversible reaction arrow)> HClO + HCl

The Cl oxidation state goes from
0 to -1 in HCl
0 to +1 in HClO

Posted from TSR Mobile

[QUOTE="OneandOnly123;56327523"]

Original post by Bloom77

Sorry!!
Didn't read the question properly

In that case

Cl2 + 2h20 --> hcl + O2

H20 = -2
O2 = 0

It's been oxidised

If I'm honest I really don't know ;/
Sorry!
It's only the chlorine that changes tbh

Cl2+h20>> hclo+hcl
0 +1 -1
the chlorine has been oxidised and reduced meaning it is a disproportionation reaction.

Thanks guys :smile:

Bloom, you're right the oxidation states of O and H remain unchanged so it's a disproportionate reaction-! Thank you. :smile:

Reply 342

9clpc9

2

Original post by Super199

Can someone explain how increasing pressure would increase the yield. Lets say the haber process and you increase the total pressure. What happens to yield and why?

In the Haber Process there are fewer gaseous moles on the RHS than the LHS so when the pressure is increased equilibrium will shift to the the right handside to oppose the increase in pressure therefore a higher yield. I hope that makes sense :smile:

Reply 343

Guls

14

Original post by couragesuccess

It is an Eisomer
The way iremember it is when you are asked for a Z isomer remember Zee iZ on Zee Zame Zide! The functional groups need to be on the same side in a Z geometric isomer. E isomers are on opposite sides!

Posted from TSR Mobile

ImageUploadedByStudent Room1432929088.449006.jpg

is this right

Posted from TSR Mobile

Reply 344

Guls

14

What are the hardest Chem 2 past papers. Really want to challenge myself ☺️

Posted from TSR Mobile

Reply 345

Spelly456

2

If the question says draw the structure can you give the displayed formula?

Reply 346

samwillettsxxx

3

Original post by Guls

is this right

Posted from TSR Mobile

Nope this is. Hope u see now :smile:

Reply 347

Dr. Swiftie

8

Original post by Guls

is this right

Posted from TSR Mobile

No that's wrong.

By "same side" it doesn't mean left or right, it means top or bottom

So for a Z isomer the two chains are both at the top or both at the bottom.

I've attached an example from the textbook

Posted from TSR Mobile

1432930821105.jpg36.0KB

Reply 348

Amyjonesx

2

could anyone explain UMS to me please?
what is the minimum UMS required in each unit to get an A overall?

Reply 349

thenextchemist

21

Original post by Bloom77

There hasn't been an exam question on electronegativity on group 7

What would you say?
For instance, the question says:
Why does chlorine have a smaller electronegative than fluorine?

Chlorine has a smaller electronegativity than fluorine because fluorine is a smaller atom than chlorine so attract shared electrons more.

Posted from TSR Mobile

Bump

Posted from TSR Mobile

Reply 350

Dr. Swiftie

8

Original post by Amyjonesx

could anyone explain UMS to me please?
what is the minimum UMS required in each unit to get an A overall?

You'd need a total of 260/300 UMS for an A

On average that is:
80/100 in unit 1
112/140 in unit 2
48/60 in the EMPA/ISA

Reply 351

Datta10

3

Original post by Dr. Swiftie

You'd need a total of 260/300 UMS for an A

On average that is:
80/100 in unit 1
112/140 in unit 2
48/60 in the EMPA/ISA

I thought you need 240/300ums fpr an A?

Posted from TSR Mobile

Reply 352

Amyjonesx

2

Original post by Dr. Swiftie

You'd need a total of 260/300 UMS for an A

On average that is:
80/100 in unit 1
112/140 in unit 2
48/60 in the EMPA/ISA

thankyou!
i definitely did not get that on my EMPA so im hoping i can bring it up with unit1/2

Reply 353

Hudl

OP

16

Original post by Dr. Swiftie

You'd need a total of 260/300 UMS for an A

On average that is:
80/100 in unit 1
112/140 in unit 2
48/60 in the EMPA/ISA

Original post by Datta10

I thought you need 240/300ums fpr an A?

Posted from TSR Mobile

You need 240/300ums for an A at AS. That is 80%ums available to you, if you do the maths, (0.80)

Reply 354

Tobiasoned

1

Original post by Super199

Can someone explain how increasing pressure would increase the yield. Lets say the haber process and you increase the total pressure. What happens to yield and why?

The equation for the haber process:

N2 + 3H2 [Equilibrium sign] 2NH3

On the reactant side, there is 3 + 1 so 4 moles.

On the product side, there is only 2

so a 4:2 ratio.

One way might be, thinking of the molar ratio as the particle ratio.(less particles in a set volume = less pressure in set volume)

Think about it like this in terms of pressure. If there are less particles in the same volume, then pressure is decreased. If you increased the pressure of the haber process, the equilibrium would move to the product side. Why? The molar ratio is 4:2, so if it moved towards the product side, then there would be less particles in the same volume, reducing the pressure again.

Going off memory, the mark scheme is usually like this

M1: Say what would happen to the yield( In this case, the yield of NH3 would increase if pressure was increased)

M2: State which side has the most/least moles.
so..
M3: Position from equilibrium moves from (in this case) left to right(towards product side, 4:2 ratio)

M4: In order to decrease the pressure(again)

I hoped i helped a bit, my grammar isn't the best so if anything doesn't make sense lemme know, also its a bit of a wall of text, sorry about that.

Oh one more thing. Tywin lannister chemistry(youtube channel) has a good video on equilibrium , i definitely recommend it and the unit 2 stuff on there in general is very good.
Same goes for E rintoul.

Reply 355

Dr. Swiftie

8

Original post by Hudl

You need 240/300ums for an A at AS. That is 80%ums available to you, if you do the maths, (0.80)

Original post by Datta10

I thought you need 240/300ums fpr an A?

Posted from TSR Mobile

Whoops you're right, I added all of them up wrong :P

But the ums for each unit is correct

(edited 8 years ago)

Reply 356

AngelaMckenzie

3

What is the difference between an ionic equation and a redox equation? What do they both show that's different?

Reply 357

Hudl

OP

16

Can someone help me with the June 2011 question 3fi)

I dont get how the answer is basically but-1-ene when if you draw it out there are 2H on the same side. I put answer as 2-Methylprop-1-ene

http://filestore.aqa.org.uk/subjects/AQA-CHEM2-W-QP-JUN11.PDF

EDIT - Because if you look at the same paper on question 6ci) the answer to that also has 2H on the same side and then CH3 and CH(OH)CH3 on the other side and it is said to be a Z stereoisomer so i dont get how the answer they gave for 3fi) is correct!

(edited 8 years ago)

Reply 358

username1006802

5

Original post by Hudl

Can someone help me with the June 2011 question 3fi)

I dont get how the answer is basically but-1-ene when if you draw it out there are 2H on the same side. I put answer as 2-Methylprop-1-ene

http://filestore.aqa.org.uk/subjects/AQA-CHEM2-W-QP-JUN11.PDF

Hi, the questions asking for a compound that does NOT show stereoisomerism, hence with but1-ene you have 2 hydrogen groups on one of the carbon atoms in the double bond. Also you wouldn't be able to put prop1ene as it's asking for a chain isomer so you know it's got to be of a different main carbon chain lengh. Hope that helps, i always get muddled too!

EDIT - just saw your edit lol. The answer to 6ci, has 2 hydrogens on the same side but they are not on the same carbon atom and that's why it's called a Z isomer. The two groups on each of the carbon atoms making up the double bond are different to one another e.g. a H and CHOHCH3 on one carbon atom and a H and CH3 on the other.

(edited 8 years ago)

Reply 359

Hudl

OP

16

Original post by zintanax

Hi, the questions asking for a compound that does NOT show stereoisomerism, hence with but1-ene you have 2 hydrogen groups on one of the carbon atoms in the double bond. Also you wouldn't be able to put prop1ene as it's asking for a chain isomer so you know it's got to be of a different main carbon chain lengh. Hope that helps, i always get muddled too!

Take a look at my edit, because on the mark scheme to that answer they allow 2H on the same side and 2 different groups on the other side and it was classified as Z. With the 3fii) but-1-ene also has 2hydrogens on the same side, although it has 2 hydrogens on 1c

h--c=c--h

Ch3Ch2 h

AQA CHEM2 2nd June 2015 [Official thread]

Related discussions

Latest

Trending

Trending

Articles for you