What volume of 0.1 M `K_2Cr_2O_7` is required to oxidise 50 " mL of " 0.2 M `Cu_2S` (cuprous sulphide) in acidic medium to give `Cr^(3+),Cr^(2+)`, and `SO_2(g)`?

Explanation

`{:(2Cu^(o+)to2Cu^(2+)+2e^(-)),(S^(2-)toSO_(2)+6e^(-)):}]"n-factor"=8`
`6e^(-)+Cr_2O_7^(2-)to2Cr^(3+)(n=6)`
`thereforeCr_2O_7^(2-)-=Cu_2S`
`1mEq-=1mEq`
`N_1V_1(mL)-=N_2V_2(mL)`
`0.1xx6` (n-factor) `xxV_1-=0.2xx8` (n-factor) `xx50mL`
`V_1=(0.2xx8xx50)/(0.1xx6)=133.33mL`