Question

Which of the following is correct representation of a given molecular equation in ionic form?
$K_{2}C{r}_2{O}_7+7H_{2}S{O}_4+6FeS{O}_4\to 3F{e}_2(S{O}_4{)}_3+C{r}_2(S{O}_4{)}_3+K_{2}S{O}_4+7H_{2}O$

• A. $C{r}_2{O}_7^{2-}+14H^{+}+6F{e}^{2+}\to 6F{e}^{3+}+2C{r}^{3+}+7H_{2}O$
• B. $2K^{+}+C{r}_2{O}_7^{2-}+7S{O}_4^{2-}+6F{e}^{2+}\to 3F{e}^{3+}+S{O}_4^{2-}+C{r}^{3+}+K^{+}+7H_{2}O$
• C. $C{r}_2{O}_7^{2-}+2K^{+}+7H^{+}+6F{e}^{2+}\to 6F{e}^{3+}+6C{r}^{3+}+K^{+}$
• D. $C{r}_2{O}_7^{2-}+7H^{+}+6F{e}^{2+}\to 3F{e}^{2+}+2C{r}^{3+}+2K^{+}+7H_{2}O$

Answer 1

Answer: (A)

$C{r}_2{O}_7^{2-}+14H^{+}+6F{e}^{2+}\to 6F{e}^{3+}+2C{r}^{3+}+7H_{2}O$

Given reaction:

$K_{2}C{r}_2{O}_7+7H_{2}S{O}_4+6FeS{O}_4\to 3F{e}_2(S{O}_4{)}_3+C{r}_2(S{O}_4{)}_3+7H_{2}O+K_{2}S{O}_4$
In ionic form :

$2K^{+}+C{r}_2{O}_7^{2-}+14H^{+}+7S{O}_4^{2-}+6F{e}^{2+}+6S{O}_4^{2-}\to 6F{e}^{3+}+9S{O}_4^{2-}+2C{r}^{3+}+3S{O}_4^{2-}+2K^{+}+S{O}_4^{2-}+7H_{2}O$

OR

$2K^{+}+C{r}_2{O}_7^{2-}+14H^{+}+13S{O}_4^{2-}+6F{e}^{2+}\to 6F{e}^{3+}+13S{O}_4^{2-}+2C{r}^{3+}+2K^{+}+7H_{2}O$

Eliminating the common species $K^{+}$ and $S{O}_4^{2-}$ from both sides of the reactions we get

$C{r}_2{O}_7^{2-}+14H^{+}+6F{e}^{2+}\to 6F{e}^{3+}+2C{r}^{3+}+7H_{2}O$

It is the ionic form of the given chemical reaction.