(Need the solutions; I got the answers) pt 2 5. A sample of a pure compound (CH

Question

(Need the solutions; I got the answers) pt 2

5. A sample of a pure compound (CH3)4NBrx weighing 0.0962 g was dissolved and treated with a reducing agent to ensure that all the bromine was present as Br-. A precipitate of silver bromide weighing 0.1730 g was obtained. Calculate the value of x in the formula of the compound.

6. Compounds of the elements yttrium (Y) and ytterbium (Yb) have very similar chemical properties and are difficult to separate. A 500 mg sample mixture containing only Y2O3 and Yb2O3 was dissolved and the combined Y3+ and Yb3+ titrated with EDTA. The results of this titration showed that the sample contained a total of 1.953 mmole of the two metal oxides. Calculate the percentage of Y2O3 and Yb2O3 in the mixture.

Answers:

5. x = 3
6. Y2O3 = 72.4%
Yb2O3 = 27.6%

Explanation / Answer

moles of AgBr formed= 0.1730/187.77=0.00092133993 moles

Moles of Br will also be same=0.00092133993 moles

so molecular mass of (CH3)4NBrx = 12*4+12+14+79.904x= 74+79.904x gm

and moles of Br in(CH3)4NBrx = X*moles of (CH3)4NBrx =(X *0.0962 )/ (74+79.904X) = 0.00092133993

(X *0.0962 )=0.00092133993*74+79.904* 0.00092133993*X

X 0.0962 = 0.0681791548 +0.0736187458 X

X= 0.0681791548 /(0.0962-0.0736187458) =3

so X=3

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