Chemistry: Post your doubts here!

[Logitech]

Anyone can give tips for titration questions

So then if you have tips for other experiments, please go ahead.

 

[AbbbbY]

Did we have to name A?

Nope. Just asked for the Ar.

 

[Anees2rehman]

I if i get 45/60 in paper 2. Can i still get an A in chemistry? Please help im worried.

 

[EddieX]

i also got x=1
the are was the problem..easiest paper ive seen :/...or i overstudied :$

 

[AbbbbY]

For the practical paper can we get to test for gases other than NH3 and how to test for them?

I think NO2 (?). It's a brown gas. The test tube turns brownish on the inside. It's given on the last page btw so just cross check from that.
O2 -> Relights a glowing splint
H2 -> Burning splint goes off with a pop
CO2 -> Turns limewater milky

What I usually advise people is to briefly smell the gas evolved. If it's ammonia, just write ammonia, don't waste your time checked for everything. If it's NOT ammonia, start with CO2 then go to O2 and lastly H2. I've never seen H2 show up. O2 twice. Ammonia A LOOOOT and CO2 quite often too.

For the Ammonia test if you end up performing it, make sure you use DAMP litimus paper or the colour wont change (Ligand exchange wont happen without water!).
Secondly, ensure that the litimus paper doesn't touch the test tube because you've already added an alkaline solution so don't want to get an incorrect result there.

 

[AbbbbY]

i also got x=1
the are was the problem..easiest paper ive seen :/...or i overstudied :$

Definitely the former. Recent P2's have been much more challenging. Anyway. The Organic will help you in P4. They might not have asked a lot of the reactions now but A2 organic is A2 inside the ring and AS outside it.

 

[Suchal Riaz]

https://www.xtremepapers.com/commun...load-post-your-doubts-here.33074/#post-758366
Readings of 2013 past papers to practice working and graphs.

 

[Suchal Riaz]

/
https://www.xtremepapers.com/commun...ook-free-download-post-your-doubts-here.33074
Practical | GUIDE BOOK(free Download) | POST YOUR DOUBTS HERE.

 

[Browny]

I think NO2 (?). It's a brown gas. The test tube turns brownish on the inside. It's given on the last page btw so just cross check from that.
O2 -> Relights a glowing splint
H2 -> Burning splint goes off with a pop
CO2 -> Turns limewater milky

What I usually advise people is to briefly smell the gas evolved. If it's ammonia, just write ammonia, don't waste your time checked for everything. If it's NOT ammonia, start with CO2 then go to O2 and lastly H2. I've never seen H2 show up. O2 twice. Ammonia A LOOOOT and CO2 quite often too.

For the Ammonia test if you end up performing it, make sure you use DAMP litimus paper or the colour wont change (Ligand exchange wont happen without water!).
Secondly, ensure that the litimus paper doesn't touch the test tube because you've already added an alkaline solution so don't want to get an incorrect result there.

Can how can we test with limewater will they provide with the tube and all?
And what if the gas is poisonous then we cant smell it, who knows whether it is SO2.

 

[AbbbbY]

Can how can we test with limewater will they provide with the tube and all?
And what if the gas is poisonous then we cant smell it, who knows whether it is SO2.

SO2 wont show up. NO2 is brown so you'll know when it shows up. Ammonia has a very distinct, pungent smell. Slightly smelling, not inhaling it all in should tell you whether it is Ammonia or not. I'm not saying you do this, just what I do and end up saving a lot of time and effort.

Never done a CO2 test in lab?

You basically take a test tube and put a lil bit of limewater in it (enough to submerge the delivery tube). Then you put the delivery tube inside and connect the stoppered end of the delivery tube righttt after mixing the reactants. If it turns milky, it's CO2, if it doesn't, it's something else. Make sure you have enough limewater inside. Limewater turns back clear on exposure to excess CO2!

 

[Browny]

SO2 wont show up. NO2 is brown so you'll know when it shows up. Ammonia has a very distinct, pungent smell. Slightly smelling, not inhaling it all in should tell you whether it is Ammonia or not. I'm not saying you do this, just what I do and end up saving a lot of time and effort.

Never done a CO2 test in lab?

You basically take a test tube and put a lil bit of limewater in it (enough to submerge the delivery tube). Then you put the delivery tube inside and connect the stoppered end of the delivery tube righttt after mixing the reactants. If it turns milky, it's CO2, if it doesn't, it's something else. Make sure you have enough limewater inside. Limewater turns back clear on exposure to excess CO2!

Why won't SO2 wont show up?

 

[AbbbbY]

Why won't SO2 wont show up?

How do you test for SO2 gas? Why would it show up if you're never taught how to test for it -_-

 

[Namehere]

How do you test for SO2 gas? Why would it show up if you're never taught how to test for it -_-

Don´t you use filter paper soaked with a bit of acidified potassium dichromate and when SO2 reaches it, it goes from orange to green? Not sure, maybe I´m wrong.

 

[daredevil]

Heyy guyss.... i am a little confused here....

so let's say that u have two hypotheticaal equations...

they have the reduction potentials of -0.15 and -1.15
which one of them will be reduced and which will be oxidised??

 

[Namehere]

Heyy guyss.... i am a little confused here....

so let's say that u have two hypotheticaal equations...

they have the reduction potentials of -0.15 and -1.15
which one of them will be reduced and which will be oxidised??

The more negative one will undergo oxidation, the more positive one will undergo reduction.

So, the -0.15 will get reduced, while the -1.15 will get oxidised.

 

[AbbbbY]

Don´t you use filter paper soaked with a bit of acidified potassium dichromate and when SO2 reaches it, it goes from orange to green? Not sure, maybe I´m wrong.

That's no longer part of the A Level practical syllabus AFAIK. They've also removed Pb ions.

 

[Suchal Riaz]

Please help me asap

 

[..sacrifice4Revenge..]

The more negative one will undergo oxidation, the more positive one will undergo reduction.

So, the -0.15 will get reduced, while the -1.15 will get oxidised.

this is A2 right? cz I dont get a word of it. :S

Please help me asap
View attachment 41543

which paper?
i'll try.

 

[Suchal Riaz]

no it's As. i have figured it out. thanks for pretending to help.

this is A2 right? cz I dont get a word of it. :S



which paper?
i'll try.

ene

 

[Namehere]

this is A2 right? cz I dont get a word of it. :S



which paper?
i'll try.

Well, you were talking about reduction potentials.. which I think is A2. Don´t listen too much to me though, I´m a very "mistaky" person...