Question

Balance the following by ion-electron method.
\[{C_2}{H_5}O{H_{\left( {aq} \right)}} + C{r_2}{O_7}{^{2 - }_{\left( {aq} \right)}} \to C{O_2}_{\left( g \right)} + C{r^{3 + }}_{\left( {aq} \right)}\]

Answer 1

Hint: The ion-electron method can be written by the sum of the reduction and oxidation half reactions.
Oxidation half reaction is the reaction in which the group or ion undergoes oxidation.
Reduction half reaction is the reaction in which the group or ion undergoes reduction.

Complete answer: A chemical reaction is the representation of conversion of reactants into products.
The oxidation half reaction is defined as the reaction in which the reactants undergo oxidation.
Oxidation is defined as the loss of electrons.
The reduction half reaction is defined as the reaction in which the reactants undergo reduction.
Reduction is defined as the gain of electrons.
These two half reactions must be balanced first.
The electrons in the two half reactions must be equal and can be cancelled out, then the common ions or groups can be written after cancelling out.
The reaction after doing the above cancellation must be written.
The obtained reaction is balanced by the ion-electron method.
Oxidation half reaction:
\[{C_2}{H_5}OH + 3{H_2}O \to 2C{O_2} + 12{H^ + } + 12{e^ - } - - - - (1)\]
Reduction half reaction:
\[C{r_2}{O_7}^{2 - } + 14{H^ + } + 6{e^ - } \to 2C{r^{3 + }} + 7{H_2}O - - - - (2)\]
Now, multiply the reduction half reaction with 2
Thus, it can be written as
\[2C{r_2}{O_7}^{2 - } + 28{H^ + } + 12{e^ - } \to 4C{r^{3 + }} + 14{H_2}O - - - - (3)\]
Now, add the two equations (1) and (3)
We will get,
\[{C_2}{H_5}OH + 3{H_2}O + 2C{r_2}{O_7}^{2 - } + 28{H^ + } + 12{e^ - } \to 4C{r^{3 + }} + 14{H_2}O + 2C{O_2} + 12{H^ + } + 12{e^ - }\]
Cancel out the \[12\] electrons on both sides.
Subtract the common groups on both sides from higher numbers.
The equation can be rearranged to
\[{C_2}{H_5}OH + 2C{r_2}{O_7}^{2 - } + 16{H^ + } \to 4C{r^{3 + }} + 11{H_2}O + 2C{O_2}\]
The above equation is the balanced chemical equation of the given chemical reaction.

Note:
The atoms must be balanced or equal on both sides of the reaction.
The reduction and oxidation half reactions must contain the same number of electrons.
The common ions or groups must be cancelled out or subtracted from a higher number of ions or groups.