Paper 5 Tips !! :)

[knowitall10]

ON/10/53
Q1 c & d
Q2 how to find the concentration of succinic acid in each layer ?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_53.pdf

You know this will be the third or fourth time this question had been asked
I suggest you look for it in the previous few pages InshAllah you'll find it. if you don't, then i'll be happy to explain again.

 

[Ash1994]

i need help in part 2 e
what does the gradient represent?
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w08_qp_5.pdf

 

[knowitall10]

For column F you use, C-B. Doesn't that give the mass of solution, and not the mass of water in the solution?

The mass of solution right here is the mass of water
1cm3 = 1g try using this principle to understand what i did. because obviously, there isnt any other way to get values less than 100 now is there?

 

[Ashique]

they say in some marking schemes that dissolve solid in lil' water first and then make up the solution to for eg, 250 cm^3 ,,,,,we dont do that here ? mixing solid in lil' water first and then making up the sol. to the required volume ?

We usually do that when we try to dilute the concentration of solution in a titration. Every situation is different, however. Could you please link me to a ms that tells us to do that?

 

[AdeleintheDeep]

Check out the second bullet point. Part iii asks us to "calculate the molar concentration of one of the solutions of copper (II) sulfate". In my second bullet point I explained how to make a 0.01 mol/dm^3 solution:


In part i, you need to state that atleast 5 or more dilutions need to be made. You could even state the concentrations. Foe eg: conc. range: 0.01, 0.05, 1.00 1.10, 1.20 and 1.39. In Part iii, you need to show how you make a solution of a certain concentration.

OH! Well that makes part i a piece of cake. thanks man

 

[mariamalik]

Ashique lemme know if its not clear

 

[FRENZYAMU]

do
lol, mass of alcohol burnt!

one more thing in calculating delta C in labarotory, do we have to calculate Q for 1 mol of CO^2 produced like in stardard enthalpy of combustions.......if so then formula wud be mc4T/moles of co^2 produced(by the calulated moles of ethanol by stoichiometry) ???
my teacher didnt give much coaching for preparing p5 nd she goes on telling looong stories

 

[knowitall10]

its

Ashique lemme know if its not clear

not clear..try writing with pen? maybe that'll help.

 

[Zari]

Ashique lemme know if its not clear

sis i have the same dbt but its not clear

 

[kitty_toxic]

ummmm well im havin ALOT of probs in dilutions, i just dont get it?!!!!

 

[Ashique]

Ashique lemme know if its not clear

It is very unclear. Could you please explain what you did? I really appreciate the help!

 

[knowitall10]

ummmm well im havin ALOT of probs in dilutions, i just dont get it?!!!!

Look at the previous pages, sister.. dilutions have been explained many times.. if you don't find it, lemme know

 

[FRENZYAMU]

We usually do that when we try to dilute the concentration of solution in a titration. Every situation is different, however. Could you please link me to a ms that tells us to do that?

it is oct/nov 2009 variant 52.......nd plz tell me now what u think

 

[kitty_toxic]

lol ok jus saw it now, thanxies ^-^

 

[kitty_toxic]

BTW all this info is suuuuuuuuuuuuuuuuuuuuuuper helpful, thnxs again, u have my duas!!!!

 

[knowitall10]

lol ok jus saw it now, thanxies ^-^

no prob

 

[kitty_toxic]

Measuring Enthalpy Change of Neutralisation!(remember we have to use calorimeter)
For this You have to have an equal amounts of both Reactants to make a solution
1) Take 150cm3 Polystyrene/Plastic cup(it is a good insulator)
2) use burette to measure 50cm3 of acid
3) Transfer 50cm3 of acid in a polystyrene cup stir it a little with thermometer and measure its acid(initial temp)
4) use another burette to measure 50 cm3 of alkali
5) Transfer it into polystyrene cup and stirr it with thermometer and measure the highest temperature
(note: cup could get hot)
now dummy Data
mass: 50cm3 + 50 cm3 = 100g
specific heat capacity=4.2
temp rise(final - initial) = (45-25) = 20*C

for heat change Q=mc4T=(100x4.2x20) = 8400J
now suppose we have acid of 1moldm-3 and alkali 1 moldm-3
then mols = ( conc/vol) = 0.05mol
0.05 mol ---> 8400J
1mol --> x
x= -168kJ (as we know reaction is exo we place a -ve sign)..

arent we supposed to conver C* to kelvin?????

 

[mariamalik]

Hope you can see it now

 

[mariamalik]

You know this will be the third or fourth time this question had been asked
I suggest you look for it in the previous few pages InshAllah you'll find it. if you don't, then i'll be happy to explain again.

Can you please explain it ???

 

[kitty_toxic]

do we have

To find the solubility of any solid dissolved in any solution
Take 250 cm3 conical flask pour 50 cm3 of water
weigh a sample of solid and add it into water and stirr it until no more solid dissolves
then leave it for sometime to cool down to give crystals
filter the solution transfer the residue and discard the saturated solution
wash the residue with distilled water thoroughly and discard water then add propanone to absorb any water droplet left
warm a little or place the container under oven or sun (not bunsen burner else it will decompse solid) to evaporate any propanone left
now weigh the residue
repeat until constant mass is acheived
substract mass if residue with the initial mass so u'll get mass of solid dissolved to make a saturated solution,
now to find solubility use ( mass of solid use x 100)/mass of water

to convert the mass of solid from g--->to kg??? sorry if im bothering alot,(extremely confused private candidate)