Decomposition of Hydrogen Peroxide | Reactions | Chemistry | The Fuse School

Summary

This lesson explores the catalytic decomposition of hydrogen peroxide using manganese dioxide, a process that produces oxygen gas. The video covers the practical uses of hydrogen peroxide, such as cleaning and hair lightening, and explains how it decomposes into water and oxygen in the presence of light and heat. By measuring the oxygen produced using a gas syringe, the reaction's rate can be plotted and analyzed. The rate is faster at the beginning and slows over time, with the gradient of the curve indicating the speed of the reaction at any given point.

Takeaways

• 🧪 Hydrogen peroxide is commonly available in dilute solutions of 3–30% by volume and has household uses like cleaning stains and bleaching hair.
• 🌞 It must be stored in a dark plastic container to prevent decomposition due to sunlight and heat.
• 💧 Hydrogen peroxide can decompose into water and oxygen because the O–O bond in the molecule is unstable.
• 📊 The decomposition of hydrogen peroxide can be monitored by measuring the volume of oxygen gas produced over time.
• ⚡ Manganese(IV) oxide acts as a catalyst to speed up the decomposition reaction.
• 🖤 When manganese(IV) oxide is added to hydrogen peroxide, fizzing occurs, indicating oxygen gas is being released.
• 🔥 The reaction is exothermic, meaning it releases heat energy.
• -
• ⏱️ The volume of oxygen can be recorded at specific time intervals to track the reaction rate.
• 📈 Plotting oxygen volume against time produces a curve where the slope (gradient) indicates the rate of reaction.
• 📐 A steeper gradient on the graph represents a faster reaction, while a shallower gradient indicates a slower reaction.
• 🚀 At the start of the reaction, the decomposition rate is very fast due to the high concentration of hydrogen peroxide.

Q & A

What is the main topic of this lesson?

The lesson focuses on how a catalyst affects the rate of decomposition of hydrogen peroxide.

What are some common household uses of dilute hydrogen peroxide?

Dilute hydrogen peroxide can be used to remove stains from furniture and clothing, and to bleach or lighten darker hair.

Why is hydrogen peroxide stored in dark plastic containers away from sunlight?

Hydrogen peroxide decomposes in the presence of warm conditions and UV light, so it is stored in dark containers to prevent this reaction.

What are the products of the decomposition of hydrogen peroxide?

Hydrogen peroxide decomposes into water and oxygen.

Why is the oxygen-oxygen bond in hydrogen peroxide considered unstable?

The bond is weak, which makes the molecule prone to breaking down into water and oxygen.

How can the rate of decomposition of hydrogen peroxide be monitored in the experiment?

The rate can be monitored by measuring the volume of oxygen gas produced over time using a gas syringe.

Which substance is used as a catalyst in this experiment?

Manganese(IV) oxide, a fine black powder, is used as the catalyst.

Why should the flask be quickly stoppered after adding the catalyst?

To prevent any evolved oxygen from escaping into the surrounding environment, ensuring accurate measurement of gas volume.

What does the fizzing observed in the reaction indicate?

Fizzing indicates that oxygen gas is being produced as the hydrogen peroxide decomposes.

How can the rate of reaction be determined from the graph of oxygen volume versus time?

By drawing a tangent to a point on the curve and calculating its gradient, which represents the rate of decomposition at that moment. A steeper gradient means a faster reaction rate.

Why is the reaction described as exothermic?

Because it releases heat energy during the decomposition of hydrogen peroxide.

How does the reaction rate change over time?

The rate of decomposition is fastest at the start of the reaction and decreases over time as the concentration of hydrogen peroxide reduces.