Calculate the percentage of Cr in a sample of dichromate ore if 1.0 g of the sample after fusion is treated with 60 " mL of " 0.1 N FeSO_(4).(NH_(4))_(2)SO_(4) and the excess of Fe^(2+) requires 11.2 " mL of " K_(2)Cr_(2)O_(3) in the sample.

Calculate the percentage of Cr in a sample of dichromate ore if 1.0 g

1.	Calculate the percentage of Cr in a sample of dichromate ore if 1.0 g of the sample after fusion is treated with 60 " mL of " 0.1 N FeSO_(4).(NH_(4))_(2)SO_(4) and the excess of Fe^(2+) requires 11.2 " mL of " K_(2)Cr_(2)O_(3) in the sample.
Answer» Solution :`6e^(-)+Cr_(2)O_(7)^(2-)to2Cr^(3+)(n=6)` `Fe^(2+)TOFE^(3+)+e^(-)(n=1)` `m" Eq of "K_(2)Cr_(2)O_(7)` in 1 mL`=m" Eq of "Fe` `=(0.006)/(56)xx10^(3)=(6)/(56)` m" Eq of "`K_(2)Cr_(2)O_(7)` in 11.2 mL`=(6)/(56)xx11.2=1.2` ltBrgt mEw of `Fe^(2+)` LEFT UNUSED`=m" Eq of "K_(2)Cr_(2)O_(7) used=1.2` Now, `m" Eq of "FeSO_(4).(NH_(4))_(2)SO_(4) added =60xx0.1=6` `m" Eq of "FesO_(4).(NH_(4))_(2)SO_(4)` left unused`=6-1.2=4.8` m" Eq of "`Cr=4.8`(`thereforeEw of Cr=(52)/(3))` `(E)/((52)/(3))xx10^(3)=4.8` `W_(Cr)=(4.8xx52)/(10^(3)xx3)=0.0832g` `% of Cr=(0.0832)/(1.0)xx100=8.32%` Also, m" Eq of "`Cr_(2)O_(3)=4.8` `(becauseEw of Cr_(2)O_(3)=(52xx2+48)/(6)=(156)/(6))` `(W_(Cr_(2)O_(3))/((152)/(6))xx10^(3)=4.8` `W_(Cr_(2)O_(3))=(4.8xx152)/(6xx1000)=0.1216g` `% of Cr_(2)O_(3)=(0.1216)/(1.0)xx100=12.16%`