Question

In the following equation
`CrO_(4)^(2-)+S_(2)O_(3)^(2-)+overset(ɵ)(O)Hto[Cr(OH)_(4)]^(-1)+SO_(4)^(2-)`
What volume of 0.2 M `Na_(2)S_(2)O_(3)` solution.
A. 30 mL
B. 80 mL
C. 20 mL
D. 60mL

Answer 1

Correct Answer - B
(i). `3e^(-)+undersetunderset(x=6)(x-8=-2)(CrO_(4)^(2-))toundersetunderset(2x=12)(2x-6=-4)([Cr(OH)_(4)]^(ɵ))`
Ew of ``CrO_(4)^(2-)=(Mw)/(3)`
(ii). `undersetunderset(2x=4)(2x-6=-2)(S_(2)O_(3)^(2-)toundersetunderset(2x=12)(2x-6=-4)(2SO_(4)^(2-)+8e^(-)`
" Eq of "`S_(2)O_(3)^(2-)=(Mw)/(8)`
`N_(1)V_(1)(CrO_(4)^(2-))=N_(2)V_(2)(S_(2)O_(3)^(2-))`
i.e., `m" Eq of "CrO_(4)^(2-)=m" Eq of "S_(2)O_(3)^(2-)`
`V_(1)xx0.2xx3=30xx0.2xx8`
`V_(1)=(30xx0.2xx8)/(0.2xx3)=80mL`