1.

You are given a 2.198 - g samplecontaining a mixture of XO and X_(2)O_(3) .It requires 0.015 mol of K_(2)Cr_(2)O_(7) to oxidise the samplecompletely to form XO_(4)^(-) and Cr^(3+) .If 0.0817 mole XO_(4)^(-)is formed ,what isthe atomic mass of X?

Answer»

Solution :
Applying POAC for X atomsof atomic mass say x ,
MOLE of `XO+2xx` mole of `X_(2)O_(3) `mole of `XO_(4)^(-)`
`m/(x+16) +(2(2.198 -m))/(2x+48) = 0.0187 ""…(1)`
Applying law of equivalence ,
eq. of XO + eq. of `X_(2)O_(3) = " eq. of " K_(2)Cr_(2)O_(7)`
`m/(x+16) xx 5 + ((2.198 -m))/(2x+48) xx 8 = 0.015 xx 6""...(2)`
SOLVING eqns . (1) and (2),
x = `100.04`


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