Chemo P5 tips

[MHHaider707]

When preparing a solution of a fixed concentration from a given parent solution of concentration , say, 2.0 mol/dm3

A. We are required to prepare a solution of concentration of 1.0 mol/dm3 with volume 250 cm3 ( the concn cannot be greater than 2 !!!!!!!!!!!!!!)
a. Add 100 cm3 of the parent solution to a volumetric flask of marking at 250 cm3
b. Top off with water to the mark of 250 cm3. Use a wash bottle for this purpose to have greater control over the addition process

When required to prepare 250 cm3 of 0.5 mol/dm3 solution of a crystal of Mr 50g

First realize that we need only 250 cm3, not 1 dm3
Now in 250 cm3 there will be: 50/4 = 12.5 g of the solid

So, first add 12.5 g of solid to 50 cm3 of water in a BEAKER ( not the volumetric flask yet). Also note that the volume of water is less than 250 cm3.
Stir properly and if the solid doesn't dissolve add more water until it fully dissolves
Then transfer the solution from the beaker to a volumetric flask. Remember to rinse the beaker with water and transfer the solution to the volumetric flask
Stopper the flask and shake properly
Finally, add the required volume of water to make the solution upto 250 cm3 USE A FUNNEL OR YOU RISK OVERSHOOTING THE MARK

Hey Zeebujha in this y did u take 12.5g of the crystals??

Should it not be 6.25?

Coz i did it like this...
Conc = 0.5 mol dm^ -3 and vol = 250 cm^ 3

so the moles required = (250 x 0.5) / 1000 = 0.125

so mass of crystals to b dissolved in 50 cm^3 = moles x Mr
= 0.125 x 50
= 6.25 g


Right?

 

[angelicsuccubus]

Did anyone compile notes for p5? Or can anyone just list all the experiments that have come up?

 

[leadingguy]

oct nov 10-53
Q2 table plz explain what should be added nd why???

conc. of succinic acid in water

then conc. of succenic acid in diethylether.

as it has been stated in part a and as wel as in part b \
that we have to find a relation between the conc. of acid in both solvents.

 

[user]

Hey Zeebujha in this y did u take 12.5g of the crystals??

Should it not be 6.25?

Coz i did it like this...
Conc = 0.5 mol dm^ -3 and vol = 250 cm^ 3

so the moles required = (250 x 0.5) / 1000 = 0.125

so mass of crystals to b dissolved in 50 cm^3 = moles x Mr
= 0.125 x 50
= 6.25 g


Right?

yup thats correct...thats probably a mistake...
btw check this file..

credits to smzimran for compiling...

 

[smzimran]

yup thats correct...thats probably a mistake...
btw check this file..

credits to smzimran for compiling...

I have corrected that in the file,
There are two possibilities:
Either
1. It is 6.25 g
Or
2. The concentration is not 0.5 mol dm-3, it is 1 mol dm-3

In the notes, i have used the 2nd alternative

 

[Utsav.]

conc. of succinic acid in water

then conc. of succenic acid in diethylether.

as it has been stated in part a and as wel as in part b \
that we have to find a relation between the conc. of acid in both solvents.

just exactly how am i supposed to do that???

 

[leadingguy]

find the no. of moles of of succinc acid that wil react wid NAOH

as we can deduce frm the frmula that the a ratio of succinic acid and naoh ntrilisation eq. is of 2:1 means 1 mole of naoh can nutralise 0.5 moles of succinic acid.

now we are given diif, volumes of NAOH and a fixed conc. of naOH

find moles of naoh i.e
n= cv
24.3 cm^3 of naoH of conc. o.10 mol.dm-3, wil give 0.0024 moles of NAOH

now divide them by 2 to get the moles of succinic acid


it wil be

o.0024 /2 = 0.0012moles of succinic acid

now find conc. of sucinic acid

c = n/v 0.0012/10cm^3 as 10cm^3 is the volume of water in which the acid is diluted (refer question)

hope u get what i said ???

 

[Aater Suleman]

P5 May/June 2010 component 52
Question 1 part c
can anyone help with the diagram???

 

[Talha]

ANY BODY PLZ TELL THE MAX. VOLUMES THESE APPARATUS CAN HOLD:

Burette
Pipette
Test tube
Beaker
Gas syringe
Gas jar
Voumetric flask
Boiling Tube

 

[leadingguy]

ANY BODY PLZ TELL THE MAX. VOLUMES THESE APPARATUS CAN HOLD:

Burette
Pipette
Test tube
Beaker
Gas syringe
Gas jar
Voumetric flask
Boiling Tube

Burette 45 to 50 cm^3
Pipette 25cm^3
Test tube not fixed but good to take not more than 5 to 6 cm^3 (max.)
Beaker 200, 500, cm63 varing
Gas syringe do not use bigger than 1000cm^3 (1dm^3) good 2 take of 500cm^3
Gas jar not fixed never asked I think just used fr collecting gas no need to mention volume
Voumetric flask 250cm^3
Boiling Tube it is some how thicker and of gr8er diameter than test tube so caries around 10 cm^3 ()never asked

 

[Usmanraufjh]

During magnesium and hydrochloric acid experiment, to avoid loss of gas do not start the experiment by dropping a piece of Mg in the container of acid!!!
Rather, use a divided flask (I would appreciate it greatly if someone explains what that actually means) or place a test tube containing the magnesium metal in the solution and pull the string to start the reaction

If a syringe gives wrong volume, it could be because the syringe got stuck during the experiment

Divided conical flask involves partition of the flask itself ... the two substances to be mixed are placed in separate chamber and reaction is started by shaking the flask so that the two substances mix ...

 

[leadingguy]

"show clearly in your calculation how the intercepts were used in the calculation of the slope."


what does this line means??? how can we show that????

refer here;
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_51.pdf
question 2 e)

 

[shamil]

is it possible that chromatography may come?

 

[Talha]

"show clearly in your calculation how the intercepts were used in the calculation of the slope."


what does this line means??? how can we show that????

refer here;
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_51.pdf
question 2 e)

means which points u used for ur calculation. show them in ur calculation of slope.

 

[leadingguy]

oh thanx alot i was really confuswd that are they talking abt y

means which points u used for ur calculation. show them in ur calculation of slope.

intrcept or else

 

[doc.ahmed]

construction lines?? what are these and how to construct them

 

[zaafer]

is it possible that chromatography may come?

its not gonna come !!

 

[mury456]

some1 explain to me dependent and independent variables ??

 

[Abdulrab]

guys can anyone just clear me one thing ? if there is a question on solubility and the question asks for plotting a graph for it and says to plot a line of best fit so if i dont plot a curve and instead plot a line of best fit !! will i loose a mark ??

 

[user]

guys can anyone just clear me one thing ? if there is a question on solubility and the question asks for plotting a graph for it and says to plot a line of best fit so if i dont plot a curve and instead plot a line of best fit !! will i loose a mark ??

aoa wr wb!

dunno..but why u wanna risk? draw a curve...if the points show that kind of trend..simple...but if they fit a line...u draw a line then