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Aqa chem 4/ chem 5 june 2016 thread

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Thank u both!! I get it now :biggrin:

You can either use both moles or both concentrations. This works because the number of moles = concentration/volume, so the factor of 1/v cancels on each side of the fraction.

Original post by SirRaza97

2d(i) You can use the concentration but that would take much longer to do but should give the same answer. You would fond the conc of each in the total volume and use that. Using mol values negates the fact that they are in equal volume so it's much easier.

2d(ii) Adding OH- will get rid of H+ ions. So equilibrium will shift to the right to make up for the loss of H+ thus more of the acid will dissociate. So the amount of HA decreases and the amount of Y- increases. Again the conc of each can be calculated but it would take longer to do.

HA mol - mol of OH added and NaY mol + mol of OH added.

Reply 301

Parallex

Original post by Superbubbles

why is it at half neutralisation point that there are equal moles of HA and A-?

Hopefully that's alright for you.

Reply 302

Lilly1234567890

how do you know when to use amino and amine when naming a compound.?

And when they say to write the equation blah blah. Is the equation always in this format : CH3CH2 or do we use molecular formula? .... ( idk if this makes sense)

Reply 303

ravichauhan11

Original post by Thisshouldbeapun

What are the conditions for the use of NaBH4 as a reducing agent to reduce aldehydes and ketones?

i stick with LiAlH4 and condition is ether

Reply 304

SirRaza97

What's the rule for naming a compound and putting in the e and when you don't put the e in? For example hexanedioic acid. When would I not put the e in?

Reply 305

SirRaza97

Original post by Lilly1234567890

amino is when there is an acid group and amine group. Amine is when there is only amine group. Amide is when there is amine group and carbonyl group.

You can write the molecular formula if you want. I suggest that you stick with the structural one though (makes it easier to see what is replacing what in the molecule)

Reply 306

nutcase13

Original post by SirRaza97

What's the rule for naming a compound and putting in the e and when you don't put the e in? For example hexanedioic acid. When would I not put the e in?

Im not sure if this is the "official" rule but i've noticed that when it is singular you leave out the e, but when it is dioc/dione/diol you use the e

Reply 307

RedDevil1997

What would the structure look like if glycine reacted with an excess of bromoethane??

Reply 308

Clovers

Original post by SirRaza97

What's the rule for naming a compound and putting in the e and when you don't put the e in? For example hexanedioic acid. When would I not put the e in?

I believe that two vowels remove the e. Other than that the e remains. Hope this helps :smile:

Posted from TSR Mobile

****k this exam

Why do you not take excess moles in this?

Reply 311

lahigueraxxx

Original post by SirRaza97

What's the rule for naming a compound and putting in the e and when you don't put the e in? For example hexanedioic acid. When would I not put the e in?

When the suffix begins with a vowel, you remove the e. E.g. -ol

When the suffix begins with a consonant, you keep the e. E.g. -dione

:smile:

(edited 7 years ago)

Reply 312

dnan

Original post by dnan

Why do you not take excess moles in this?

Never mind it's because there isn't OH- added but salt

Reply 313

DelwinJ98

http://filestore.aqa.org.uk/subjects/AQA-CHEM4-QP-JAN12.PDF
Can someone explain 6biii
Mark scheme
http://filestore.aqa.org.uk/subjects/AQA-CHEM4-W-MS-JAN12.PDF

Reply 314

hopingmedicinae

Original post by DelwinJ98

http://filestore.aqa.org.uk/subjects/AQA-CHEM4-QP-JAN12.PDF
Can someone explain 6biii
Mark scheme
http://filestore.aqa.org.uk/subjects/AQA-CHEM4-W-MS-JAN12.PDF

if you go back a few pages, I explain this, take a look if it's any help!

Reply 315

Thisshouldbeapun

Original post by ravichauhan11

i stick with LiAlH4 and condition is ether

thanks

Reply 316

emma_1111

What do we need to know about chromatography?

Reply 317

Mriffin

Likelyhood of a chromatography question coming up tomorrow?

Reply 318

dnan

Original post by Mriffin

Likelyhood of a chromatography question coming up tomorrow?

Original post by emma_1111

What do we need to know about chromatography?

Very likely it comes up, not likely that it is over 5 marks worth on it.

Mobile phase, Stationary phase, what the solvent does, why is it used. How it distinguishes. Different types.