Paper 5 Tips !! :)

[xhizors]

salaaaam, this is a priceless thread xhiroz
with our prayers u r gna get ur world distinction, insha Allah.
Jazakhallah brother

JazakAllah!!

 

[Haniya Khan]

Asslamu Alykum Sis.
You use the formula C1V1=C2V2.
The total volume of your solution is to be kept constant, say 50cm3. And you are to make dilutions of a given concentration, say 2.00 moldm3.
So you first decide which concentrations you want to make. marking schemes usually prefer a minimum of five concentrations, so:
1.00, 1.20, 1.40, 1.60, 1.80, and 2.00.
If you're going to make the 1.00moldm3 conc, look at the following steps:
C1V1=C2V2
C1= 2.00 (the concentraiton you're given.)
V1= x (what the volume of the new concentration will be)
C2= 1.00 (the conc you're planning to make)
V2= 50 (the total volume)
So, 2x= 1 x 50
x= 25
So now that your V2 is 25, to know what volume of water you must add to make it up to that conc, 5o-25= 25.
So your procedure to make 1.00 moldm3 from the given 2.00moldm3 would be to add 25cm3 of water into 25cm3 of acid.
Got it?

THANKYOUUU SO MCH FR THE HLP. THANKS AGAIN
YEH GOT IT

 

[xhizors]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_52.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_ms_5
Question 3 (a) how to find the mass of copper combined with 1g of oxygen?

C-B= mass of oxygen
C-A= mass of Cu
for 1st row
0.6g oxygen --> gives 1.56Cu
1g Oxygen---> x
use unitry baba

 

[Soldier313]

Can someone please have a look at qn 3 a of this paper?
I don't get how the qn a iii is asking for mass of Cu with 1 g of O, and then suddenly, it's like Cu:O ratio?
and also, why are these answers of a iii to 4 significant figures??

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_52.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_ms_52.pdf

Thanx a lot
JazakAllah khair!

anyone?

xhizors
knowitall10
MaxStudentALevel
Jiyad Ahsan
@ all other p5 candidates

EDIT: okay so xhizors already answered the first part to my qn, but the second part, why the 4 significant figures??

 

[zsyed94]

You guys should look though the last 20 pages of "Chemistry post your doubts here" main page. I've explained that very extensively there!

Hey.I looked through the pages and I didn't find anything Can you please tell me how to fill the columns? I know that we have to find the moles of NaOH and then convert them into moles of succinic acid but I don't know how to change them to moles of succinic acid and then how to find the concentration.PLEASE help me out :/

 

[Jiyad Ahsan]

anyone?

xhizors
knowitall10
MaxStudentALevel
Jiyad Ahsan
@ all other p5 candidates

EDIT: okay so xhizors already answered the first part to my qn, but the second part, why the 4 significant figures??

wait wait wait... where does it say you have to give your answers to 4 sig.figs !!?? its says 4 sig.figs in Q2.. not Q3

 

[Boss.Mentalist.Awesome]

okay i'll try to clear out the difference thing is you can use c1v1=c2v2 in both
the difference being though, is that.. lets say you start out with a solution of say HCl of 10mol/dm^3
in serial dilution you take a volume of that solution say 10 cm^3 then you add 10cm^3 of water you have a solution now that is 5mol/dm^3 HCl with a total volume of 20 cm^3
now take 10cm^3 of the solution you just made ( 5mol/dm^3 ) and add 10 cm^3 of water again.. now you have a 20 cm^3 of 2.5 mol/dm^3 HCl.. basically in serial dilution you use the solution last you made and use some of it to make a new concentration..

while in normal dilution you take 2 beakers containing 10 cm^3 each, of 10 mol/dm^3 of HCl and in one you add 10 cm^3 of water and in the other you add 30 cm^3 of water..
the result is the same.. just the difference that in normal you use the original concentration
hope it helped

JazakAllah Khair...thank you very much

 

[Daisy_94]

(d) Design a laboratory experiment that you would use to investigate your prediction in (a).
The following materials are to be used in your plan.
0.60 mol dm–3 potassium iodide
0.20 mol dm–3 potassium persulfate
0.01 mol dm–3 sodium thiosulfate
distilled water
starch indicator solution
A first experiment is carried out using the following quantities.
20 cm3 potassium iodide
40 cm3 potassium persulfate
20 cm3 sodium thiosulfate
0 cm3 distilled water
10 cm3 starch indicator solution
Give a step-by-step description of the method you would use in further experiments.
Include the following in your plan.
• the range of concentrations
• the volume of each solution to be used
• the method of measuring the volume of each solution
• how and when the solutions are to be mixed
• the way in which the dependent variable will be measured
• the control of all other variables
......................................................................................
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_qp_51.pdf
Q1(d)
Pls explain the c1v1=c2v2
• the range of concentrations
how do I do this.........................Help wud b appreciated

 

[knowitall10]

Ah sorry dude, I aint got time to search through the last 20 pages... D=
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_53.pdf
q 1(c) and question 2a, thanks!

I didnt look at the mark scheme yet for q1 c but this is my diagram:
For the next question:
the two stated volumes of the water layer and ether layer can be taken as the volume of succininc acid.
so to find it's conc in the water layer (column D), we have to realize that 1mol of NaOH=2mol of succinic acid. because NaOH has one OH gp whereas succinic acid has two OH gps.
So.. B x 0.1= 2( D x 10)
therefore, 0.1/20 B= D
You apply the same method for the conc of succinic acid in ether.
Got it?
I'll check the marking scheme for my diagram...

 

[knowitall10]

In enthalpy related reactions, do we leave the lid of the container open? Im confused. Which reactions require the container to be open? As in letting the gas escape.

Nooooooo!!!! ESPECIALLY ENTHALPY CHANGES!!! we have to prevent heat loss by covering the apparatus with a lid!

 

[Soldier313]

wait wait wait... where does it say you have to give your answers to 4 sig.figs !!?? its says 4 sig.figs in Q2.. not Q3

yess!! so how do we know now?!

 

[Jiyad Ahsan]

exactly!

thats what im saying man... you dont have to give the answer to 4 significant figures.. give it to "2 DECIMAL PLACES !!!"

 

[knowitall10]

yess!! so how do we know now?!

I don't really know this... i have a bad habit of attempting without the ms.. so i always assume that i'm probably right :/

 

[Jiyad Ahsan]

yess!! so how do we know now?!

give it to the same number of decimal places as the information given.. everything in the table is to 2 decimal places right? so give it to two decimal places

 

[Soldier313]

thats what im saying man... you dont have to give the answer to 4 significant figures.. give it to "2 DECIMAL PLACES !!!"

dude! chill!
look at that column, where the values are 2.600, 3.983......
that looks like 4 sgf to me not 2 dp!

 

[VelaneDeBeaute]

Nooooooo!!!! ESPECIALLY ENTHALPY CHANGES!!! we have to prevent heat loss by covering the apparatus with a lid!

I guess we try to 'minimise' not 'prevent' the heat loss by using a lid. The usage of lid can be tricky sometimes. For instance, in a situation where you have to add a solid to the acid contained within the cup, you cannot just add it all at once and cover the cup.

 

[knowitall10]

give it to the same number of decimal places as the information given.. everything in the table is to 2 decimal places right? so give it to two decimal places

I like this post.. i'm actually saying it

 

[Jiyad Ahsan]

look dont over-complicate stuff.. do what makes sense.. ALWAYS use the same number of sig.figs or decimal places as the information in the question UNLESS stated otherwise

 

[knowitall10]

dude! chill!
look at that column, where the values are 2.600, 3.983......
that looks like 4 sgf to me not 2 dp!
View attachment 25406

Oui... u gotta a point...

 

[knowitall10]

look dont over-complicate stuff.. do what makes sense.. ALWAYS use the same number of sig.figs or decimal places as the information in the question UNLESS stated otherwise

and u have a point too.. i don't know where i'm getting....