Please help me =)

Question

Please help me =)

kkutie7 · Answer

how to I get the grams of an unknown from titrating it against a primary standard?

cuanchi · Answer

you have to know something about the unknown, at least the molecular mass and how it is the reaction with the primary standard

kkutie7 · Answer

All I know is that I collected a sample containing iron oxide. The sampled was .3545g
10mL of nanopure water, 10mL 12 M HCL, 2.0 M SnCl2 (this was done dropwise so I have no idea how much), .2M mercury (II) chloride, 100 mL of nanopure water and 10 mL 1:2 M H2SO4/16 M H3PO4. The primary standard was a stock solution with the concentration of 54.9278 g/L it was diluted to 250 mL of .018 M K2Cr2O7.

kkutie7 · Answer

it took 27.91 M to do the titration

kkutie7 · Answer

* mL

kkutie7 · Answer

this is redox by the way

cuanchi · Answer

I am trying to figure out what is the reaction do you have a reference book o lab manual?

cuanchi · Answer

K2Cr2O7 it is your primary standard?

cuanchi · Answer

You want to determine the Fe concentration in your sample?

cuanchi · Answer

something like this experiment? http://staff.buffalostate.edu/nazareay/che112/chromate.htm

cuanchi · Answer

Cr2O72- + 6 Fe2+ + 14H+ → 2Cr3+ + 6 Fe3+ + 7H2O

cuanchi · Answer

All the Fe in the sample is first converted to Fe2+then the Fe2+ titrated by K2CrO72-

anonymous · Answer

biily

kkutie7 · Answer

yes that looks right but were did the K2 go in the overall reaction?

cuanchi · Answer

it is an spectator ion if you put Cr207k2 in the reactants you can add 2K+ in the products and it is not going to affect the 6e- exchange per mol of Cr207k2. And the same number of atoms and charge in both sides (26+)

Cr2O7K2 + 6 Fe2+ + 14H+ → 2Cr3+ + 6 Fe3+ + 7H2O + 2K+