Question

A common demonstration in chemistry courses involves adding a tiny speck of manganese(IV) oxide to a concentrated hydrogen peroxide \(\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)\) solution. Hydrogen peroxide decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese(IV) oxide is a catalyst for the decomposition of hydrogen peroxide and is not consumed in the reaction. Write the balanced equation for the decomposition reaction of hydrogen peroxide.

Short answer

The balanced equation for the decomposition reaction of hydrogen peroxide is: \[2\,\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\,\mathrm{O}_2 + 2\,\mathrm{H}_2\mathrm{O}\]

Step-by-step solution

1. Write the unbalanced equation

Write the unbalanced equation for the decomposition reaction of hydrogen peroxide: \[\mathrm{H}_2\mathrm{O}_2 \rightarrow \mathrm{O}_2 + \mathrm{H}_2\mathrm{O}\]

2. Balance the equation

In the unbalanced equation, we have 2 oxygen atoms on the left side and 3 on the right side. Also, there are 2 hydrogen atoms on the left side and 2 on the right. To balance the equation, we need to adjust the coefficients of the molecules. Multiply the water molecule by 2 to balance the number of hydrogen and oxygen atoms: \[2\,\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\,\mathrm{O}_2 + 2\,\mathrm{H}_2\mathrm{O}\] Now we have 4 oxygen atoms and 4 hydrogen atoms on both sides of the equation, so it is balanced.

3. Write the balanced equation

The balanced equation for the decomposition reaction of hydrogen peroxide is: \[2\,\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\,\mathrm{O}_2 + 2\,\mathrm{H}_2\mathrm{O}\] This equation shows the conversion of hydrogen peroxide into oxygen gas and water vapor, with the catalyst manganese(IV) oxide not appearing in the balanced equation.