Question

Which of the following is correct representation of a given molecular equation in ionic form?

}{3Fe_{2}(SO_{4})_{3} + Cr_{2}(SO_{4})_{3} + K_{2}SO_{4} + 7H_{2}O}$$

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

Answer 1

Answer: (A)

$Cr_{2}O_{7}^{2 -} + 14H^{+} + 6Fe^{2 +} \rightarrow 6Fe^{3 +} + 2Cr^{3 +} + 7H_{2}O$

Answer 2

: $K_{2}Cr_{2}O_{7} + 7H_{2}SO_{4} + 6FeSO_{4} \rightarrow 3Fe_{2}(SO_{4})_{3}$

$+ 7H_{2}O + K_{2}SO_{4}$

In ionic form:

$2K^{+} + Cr_{2}O_{7}^{2 -} + 14H^{+} + 7SO_{4}^{2 -} + 6Fe^{2 +} + 6SO_{4}^{2 -}$

$\rightarrow 6Fe^{3 +} + 9SO_{4}^{2 -} + 2Cr^{3 +} + 3SO_{4}^{2 -} + 2K^{+} + SO_{4}^{2 -} + 7H_{2}O$

Eliminating the common species:

$Cr_{2}O_{7}^{2 -} + 14H^{+} + 6Fe^{2 +} \rightarrow 6Fe^{3 +} + 2Cr^{3 +} + 7H_{2}O$