Question

Which of the following is correct representation of a given molecular equation in ionic form?
$K_{2}Cr_{2}O_{7} + 7H_{2}SO_{4} + 6FeSO_{4} \to 3Fe_{2}\left(SO_{4}\right)_{3 }+Cr_{2}\left(SO_{4}\right)_{3} + K_{2}SO_{4} + 7H_{2}O$

• A. $Cr_{2}O_{7}^{2-} + 14H^{+} + 6Fe^{2+}\to 6Fe^{3+} + 2Cr^{3+ }+ 7H_{2}O$
• B. $2K^{+} + Cr_{2}O_{7}^{2-} + 7SO^{2-}_{4} + 6Fe^{2+} \to 3Fe^{3+} +SO_{4}^{2-} + Cr^{3+} + K^{+} + 7H_{2}O$
• C. $Cr_{2}O^{2-}_{7} + 2^{K+} + 7H^{+} + 6Fe^{2+} \to 6Fe^{3+} +6Cr^{3+} + K^{+}$
• D. $Cr_{2}O^{2-} + 7H^{+} + 6Fe^{2+} \to 3Fe^{2+} + 2Cr^{3+} +2K^{+} + 7H_{2}O$

Answer 1

Answer: (A)

$K_{2}Cr_{2}O_{2} + 7H_{2}SO_{4} + 6FeSO_{4} \to$
$ 3Fe_{2}\left(SO_{4}\right)_{3} + Cr_{2}\left(SO_{4}\right)_{3} + 7H_{2}O + K_{2}SO_{4}$
In ionic form :
$2K^{+} + Cr_{2}O_{7}^{2-} + 14H^{+} + 7SO_{4}^{2-} + 6Fe^{2+} + 6SO_{4}^{2-} \to$
$6Fe^{3+} + 9SO_{4}^{2-} + 2Cr^{3+} + 3SO_{4}^{2-} + 2K^{+} + SO^{2-} + 7H_{2}O$
Eliminating the com m on species:
$Cr_{2}O^{2-}_{7} + 14H^{+} + 6Fe^{2+} \to 6Fe^{3+} + 2Cr^{3+} + 7H_{2}O$