Qualification > Sciences

CHEMISTRY. P3. CIE.. advice and titrations?

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Phosu:
i) for first step they have given u the concentration, ur titre value is the vol of Na2S2O3
so to find moles apply n=cv, n= .15 x titre/1000

ii) next is simple mole ratio which can be found from the equations
S2O32- : I2
  2 : 1
  i) : x

iii) again its the same as above
Cu2+ : I2
  2 : 1
  x : ii)

iv) now we know the moles present in Cu2+ and we have the volume (25cm3 dissolved in FA3)

  iii) = c x 25/1000

v) im not really sure bout this one

ruby92:
M/j 2009 variant 32
c step 3 4 5???

aldehyde1612:
im not sure but i think the last step involves C1*V1 = C2*V2

so.. concentration of FA2 = concentration of FA3*Volume (250 or something) divided by Volume of FA2 buretted (the amount at the beginning when making FA3)

if that makes sense.  :-\

superduper2009:
how do find water of crystallization???

XaM!!:
For water of crystallisation just follow the instructions... basicaly a test tube and a salt is given. a specific mass is asked. first u have to find mas of empty test tube. thn add salt and measure mass(mass is gven in ques whch u have to take).
now heat the test tube at medium flame. do it for 5-8 mins to ensure water is eliminatd. nw cool the tube n measure mas. again heat the test tube for another 5mins n cool n measure, thn compare if masses r the same as the recent one thn all the water is eliminated... if the mas is change thn again heat n measure mass. when it becomes constant. nw use this mass for further calculations to calculate X in salt.X.H2O... that x is water of crystallisation...

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