- #1
Buffu
- 849
- 146
Homework Statement
Balance :-
$${Cl_2O_7} + {H_2O_2} {\longrightarrow} {ClO_2^-} +{O_2} + {H^+}$$
Medium :- basic
Homework Equations
The Attempt at a Solution
$${\stackrel{+7}{Cl_2}\stackrel{-2}{O_7}} + {\stackrel{-1}{H_2}\stackrel{-1}{O_2}} {\longrightarrow} {\stackrel{+3}{Cl}\stackrel{-2}{O_2^-}} +{\stackrel{0}{O_2}} + {\stackrel{+1}{H^+}}$$
Since both Oxygen and Chlorine reduces, but Oxygen also oxidizes in equation,
$${(1/2)\stackrel{+7}{Cl_2}\stackrel{-2}{O_7}} + {\stackrel{-1}{H_2}\stackrel{-1}{O_2}} + 3{\stackrel{-1}{H_2}\stackrel{-1}{O_2}} {\longrightarrow} {\stackrel{+3}{Cl}\stackrel{0}{O_2^-}} +{3\stackrel{-2}{O_2}} + {\stackrel{+1}{H^+}}$$
After that i balanced Oxygen and Hydrogen to get
$${Cl_2O_7} + {8H_2O_2} + 2OH^- {\longrightarrow} {2ClO_2^-} +{6O_2} + {9H^2O}$$
$$
\begin{array}{c|c|c|}
\text{Element} & \text{RHS} & \text{LHS}\\
Cl & 2 & 2\\
\hline
H & 18 & 18\\
\hline
O & 25 & 25\\
\end{array}$$
But given answer is something else,
$${Cl_2O_7} + {4H_2O_2} + 2OH^- {\longrightarrow} {2ClO_2^-} +{4O_2} + {5H^2O}$$
$$
\begin{array}{c|c|c|}
\text{Element} & \text{RHS} & \text{LHS}\\
Cl & 2 & 2\\
\hline
H & 10 & 10\\
\hline
O & 17 & 17\\
\end{array}$$
Both equations seems balanced but i don't understand why ?
Also http://www.webqc.org/balance.php says there are infinite ways to balance this equation.
So how can I get the second equation instead of mine with Oxidation Number method ?