Question

Consider the following reaction, $5H_2{O}_2+xCl{O}_2+2O{H}^{-}\to xC{l}^{-}+y{O}_2+6H_{2}O$. The reaction is balanced if __________.

• A. $x=5,y=2$
• B. $x=2,y=5$
• C. $x=4,y=10$
• D. $x=5,y=5$

Answer 1

The correct option is B $x=2,y=5$

Oxidation half reaction: $H_2{O}_2\to O_2$

Reduction half reaction: $Cl{O}_2\to {Cl}^{-}$

Balance charge by adding electrons, we get

$Cl{O}_2+5e^{-}\to {Cl}^{-}$
$H_2{O}_2\to O_2+2e^{-}$

Now balance oxygen atoms by adding $H_{2}O$ and balance hydrogen atoms by adding $H^{+}$ and also balance charge by adding electrons, we get

$Cl{O}_2+5e^{-}+4H^{+}\to {Cl}^{-}+2H_{2}O$ ----- 1
$H_2{O}_2\to O_2+{2e}^{-}+2H^{+}$ ---- 2

Multiply (1) eq by 2 and (2) eq by 5, we get

$2Cl{O}_2+5H_2{O}_2\to {2Cl}^{-}+5O_2^{-}+2H^{+}+4H_{2}O$

As this reaction takes place in an alkaline medium so add $O{H}^{-}$(equal in number to $H^{+}$) on both sides, we will get

$2Cl{O}_2+5H_2{O}_2{+2OH}^{-}\to {2Cl}^{-}+5O_2^{-}+6H_{2}O$

So, $x=2,y=5$