AS Chem...Paper 34...post your doubts here...

[angelgirl:)]

hope together we can solve eachothers doubts...InshaAllah...

 

[Saad (سعد)]

As-Salaamu 'Alaykum

What are the criteria that are to be kept in mind when drawing a graph in Chem Practicals... you know the kind of graph in which there are two lines, and they are interpolated at a point where they cut each other in an X-shape... those graphs.

How do Examiners mark them? o.o Cuz I've seen past papers where that graph carries lots of marks. o.o

 

[i love my country]

guys i have a problem i cannot under stand this part in ppr3 part e


(e) 1 mol of iodine is displaced by 1 mol of ‘free chlorine’.
Cl 2(aq) + 2I–(aq) → 2Cl –(aq) + I2(aq)
Calculate the ‘free chlorine’ concentration, in moldm–3, of FA1, the bleach ‘Superclean’.

can u explain please ......

 

[angelgirl:)]

sorry ppl iam busy with p4 chem right now...i will start p3 tomo after ...so cant help any1 at the moment now...

 

[workaholic]

lol........p3 is on thursday........exam tension seems to be getting you.............

 

[angelgirl:)]

lol........p3 is on thursday........exam tension seems to be getting you.............

lol soorry... i meant tomo..wednesday...

 

[angelgirl:)]

lol........p3 is on thursday........exam tension seems to be getting you.............

anyways thanks ...

 

[workaholic]

guys i have a problem i cannot under stand this part in ppr3 part e


(e) 1 mol of iodine is displaced by 1 mol of ‘free chlorine’.
Cl 2(aq) + 2I–(aq) → 2Cl –(aq) + I2(aq)
Calculate the ‘free chlorine’ concentration, in moldm–3, of FA1, the bleach ‘Superclean’.

can u explain please ......

u need to use your answer to d * (250/25)*(1000/25)
-In the above eqn you are given that one mol of iodine is produced by one mole of free Cl2
-In the previous part u calculated the moles of I2 that reacted with the thiosulfate ions.....these are the equal to the moles of I2 displaced by free chlorine in their reaction with KI.......
-thus moles of free chlorine in 25 cm3 of FA3=moles of I2 in D
-therefore moles of free chlorine in 250cm3 of Fa3(i.e moles in the graduated flask)=(250/25)* ans in (d)
-the ans you calculated above gives you the moles 25cm3 of FA1 that you diluted by making it up to 250 in the flask....you now need to find its conc
-use the formula conc=(moles)/volume(dm3)
i.e (ans above)/(25/1000))
summing up ans=answer to d * (250/25)*(1000/25)..........
This qst was sorta difficult to explain but ive given it my best shot.......if you cant understand still maybe someone else can explain better.........Cheers........

 

[Student12]

does anyone have notes for AS practicles ?

 

[i love my country]

thanks for your explaination u really tried to explain it good
and best of luck for che practical paper 34