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A 1.85 g sample of an arsenic- containi...

A 1.85 g sample of an arsenic- containing pesticide was chemically converted to `AsO_(4)^(3-)` (atomic mas of As= 74.9) and titrated with `Pb^(2+)` to form `Pb^(3) (AsO_(4))_(2)` mL. of 0.1 M `Pb^(2+)` is required to reach the equivalence point, the mass percentages fo arsenic in the pesticide sample is closest to

A

8.1

B

2.3

C

5.4

D

3.6

Text Solution

Verified by Experts

The correct Answer is:
c
`3pb^(2+)+2ASO_(4)^(-3)to pb_(3)(AsO_(4))_(2)`
`n=MxxV " " n=2/3xx2xx10^(-3)`
`0.1 xx 20/1000=0.000133`
`2xx10^(-3)`
`eta_(AS)=eta_(ASO_(4)^(3-))=0.00133`
`W_(AS)=0.00133xx74.9=0.0996`
`%"of AS"= (0.0996)/1.85xx100=5.4%`
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