Chemistry: Post your doubts here!

[daredevil]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_4.pdf
Could someone please help me with qn no 2(e)? I don't understand why the order with respect to H+ is 0

w.r.t. H2O2 :
0.70/.05 = 1.4/1.0
7/5 = 7/5

w.r.t. H+ :
if we consider the conc of H2O2 first and compare it with rate:
0.09/0.05 = 1.8/1.0
9/5 = 9/5

it shows that the rate is changing just because of H2O2 .... which means that however much the conc of H+ changes, it won't have any effect on the rate of reaction. so wrt H+ the order of reaction is 0

 

[ZaqZainab]

Explain in detail plz, Idk anything in this quest. :'(

Okay so i just did 5 there isn't anything up with it all you have to do it study from the course book

 

[Thought blocker]

k

Okay so i just did 5 there isn't anything up with it all you have to do it study from the course book

 

[ZaqZainab]

k

 

[Thought blocker]

ty

 

[Abdel Moniem]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s09_qp_2.pdf
Question 4bii

 

[immie.rose]

I´ve already answered this question a few times... Anyways. Here what you should be careful with is the accuracy. Maintain it with 3sf. So once you divide by the smallest number and get 1 : 1.33: 1.16 ratio you just have to convert these numbers into integers. You do it through trial and error until you get all integers. If you times everything by 6 you get an integer (or atleast really close to it).

Hope it helps.

sure helped! THANK YOU!!

 

[immie.rose]

I will follow through the question from beginning to let you know how examiner give you hints.

pattern:
-(information)
the deduction we can make from information

the alcohol will oxidise to produce aldehyde and then will produce carboxyllic acid. as a single compound is formed, both carboxylic acid from ester and oxidised form alcohol are same. the only option we are left with is ethyl ethanoate. which will hydrolyse to ethanol and ethanoic acid. ethanol will then oxidise to ethanal. ethanal will oxidise to ethanoic acid. as the test for C=O and CHO are negative there is no aldehyde. the only thing left is ethanoic acid.

i hope it clears the confusion and helps in reaching conclusions in similar questions.
good luck for the papers ​

Could you pls pls explain a bit further as to why it can't be methyl ethanoate, Or propyl ethanoate, hence leaving ethyl ethanoate as the only option? thanks!

 

[AbbbbY]

Um for silicon chlorides reaction with water, do we write Si(OH)4 as the product, or SiO2,?

They're both acceptable, but the preferred product is SiO2

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_2.pdf
Question 4bii

C = CH2(OH)CH(OH)COOH
E = CH3COO-

C+E = esterification. CH2(OOCCH3)CH(OOCCH3)COOH. Another way of writing this is CH2(OCOCH3)CH(OCOCH3)COOH but this OCO shiz always confuses me so I stick to the OOC usage.

 

[WaqarAhmedJamali]

this question came in to our mock exam

 

[loveyuan]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s13_qp_13.pdf

question no 14 .
Answer C. Q only
It is because the AgCl is insoluble in NH3 so it's solubility suppose to be 0 ?

Question no 18
Answer A. CNO-

Question no 28
answer C

Thank you in advance

 

[Snowysangel]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s13_qp_13.pdf

question no 14 .
Answer C. Q only
It is because the AgCl is insoluble in NH3 so it's solubility suppose to be 0 ?

Question no 18
Answer A. CNO-

Question no 28
answer C

Thank you in advance

I though chlorides were soluble in ammonia and that upsides weren't ..

 

[loveyuan]

I though chlorides were soluble in ammonia and that upsides weren't ..

Oh yea. Thanks !

 

[Snowysangel]

Oh yea. Thanks !

Haha sorry I meant iodides...autocorrect -.-

 

[goodluckayesha]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_42.pdf
can any1 explain 3b plz?

 

[NidaChaudhary]

Can any 1 HELP??? Nov 2008 P4 Q4 B iii

 

[robinhoodmustafa]

1-

2-

3-

4-

Anybody help me in this.

Suchal Riaz

 

[Browny]

Can anybody tell me whether all the workings are needed in the calculations(especially titrations) in paper 3?
In marking schemes they put all steps into 1 working step.

 

[Mohammed salik]

Can anybody tell me whether all the workings are needed in the calculations(especially titrations) in paper 3?
In marking schemes they put all steps into 1 working step.

look at Highlighted Parts!!

 

[Browny]

View attachment 40711

look at Highlighted Parts!!

Problem is should we show the workings step by step because in some papers there are questions to calculate the moles and then the concentration in same part.
If we want we can simplify and write it down in one step like the marking scheme does. But what should we do actually simplify or write it step wise?

And another question is H2O2 a oxidising agent or a reducing agent and why?

One more, is silver sulfate a prercipitate? Because when doing a paper i thought that if their is a sulfate ion if we test that for Cl-(although it doesn't have) we might get a white precipitate if silver sulfate is ppt. and that might mislead us to thinking it has a Cl- ion.