Chemistry P34. What i know

[jafar]

^ i like ur name. bohat lushpush hai..

 

[girlscampisra]

umm, i can't get second part.. where the question says to calculate the moles of KMnO4 pipitted out of graduated flask..
will the ans be.. ANSWER TO PART (i) x 25/250 ??

 

[Feelguud77]

Dude, umm yeah yer info matches mine
The cations Aluminium, Zinc and Lead are confirm! I've kinda given my Chem.33 practical ( *posted the details too ) and i asked around about the 34 variant, and the amalgamation of what the sources say adds up

 

[jafar]

look in frst part u'll first find out the concentration by dividing 28.44mol/dm^3 by the Mr of KMnO4 which is 158
den v'll apply c = n/v

c= 0.18 mol/dm^3
v = 41 - 41 cm^3 ( whatever u took in part (a)

m= .00747

we will get the moles of KMnO4 by this

den in second part its asked in 250 cm^3 so we will use ratio

.00747------------250
x----------------25
cross multiply

 

[girlscampisra]

thanks man!! )

 

[jason3991]

WOW! ur amazing man thx....also..um how do we distinguish between lead and aluminium ions?????and also...the burette reading we write to 2 decimal places right??? so if we get a reading like 23.4 , can write it as an "impossible" reading like 23.42??? or should we leave it as 23.40.... OR... do we round to the nearest 0.05 so wud it be like 23.45??cus thats what we do with temperature right? we round to nearest 0.5..

 

[airborne1944]

for oct 08 paper 32, first question part c and the third question(with the 2 equations eg; MnO...) how to solve that?

 

[girlscampisra]

round off nearest to 0.5 do not write impossible reading! and yes lead and aluminium ions can be distinguised by adding dil. sulfuric acid.. lead ppt is insoluble in acid while Aluminium ppt is soluble!

 

[jafar]

to differentiate b/w lead and aluminium : add any chloride for eg barium chloride.. lead chloride is insoluble whereas Aluminiom chloride is soluble...

bout the burette.. if ur gettin a reading between 23.4 and 23.5 u'll take 23.45,..

 

[Feelguud77]

The only extra thing i'm hearin is titration is of KMnO4 with sodium thiosulphate,
and the rate of reaction question involves placing a paper with an 'X' mark beneath a flask in which the solution turns cloudy and you have to note that time!

 

[jafar]

titration oct/nov, 2008 paper 32 q1 is titration of thiosulphate wid KMnO4

nd may june 2003 qs 1 is the 'X' mark one!! chek out the papers i hav mentioned in my 1st comment

 

[Feelguud77]

Well then, X marks the spot "dude from Cressida Cowell's novel"

 

[airborne1944]

for oct 08 paper 32, first question part c and the third question(with the 2 equations eg; MnO...) how to solve that?

Anyone can help??? PLS

 

[jafar]

@ feelguud77 lol, my friends say dat i look lyk him, specially my hair..

 

[jafar]

@airborne.. u jus hav to use the mole ratio in these equations!

 

[Feelguud77]

*sigh* people in multan rarely know about cressida cowell, let alone the dude with the hair

 

[jafar]

everyone watches the movie..

 

[airborne1944]

must i balance the equation since the no. of electrons are diff?

 

[jafar]

it will be like this
since 5 e- in MnO4 eq nd 1 in I-
ans since I2 has half moles
so
5/2 moles of I2 give one mole of MnO4
cross multiply

2.5..........1
x............0.000747

 

[Feelguud77]

Especially the helmet giving part