The Hydrogen Peroxide is constantly being broken down but at a slow rate. With the help of the catalyst, Manganese Dioxide this will speed up the decomposition of the Hydrogen Peroxide. Hydrogen peroxide typically decomposes to form water and oxygen at the rate of 10% per year.
Here is the word equation for the reaction that I have just described:
HYDROGEN PEROXIDE WATER + OXYGEN
MANGANESE DIOXIDE
Another way of describing this equation is in a balanced chemical equation:
2H2O 2H2O + O2
MnO2
Variables
There are many things involved in this investigation, which could affect the speed the speed of this investigation. These called the variables. These variables consist of the surface area, the concentration, and the use of a catalyst, the amount of the catalyst and also the temperature. Heat, light, or a catalyst can accelerate the reaction.
- Surface area - If the Manganese Dioxide has a large surface area increases the speed of the reaction because there will be more space covered by the Manganese Dioxide resulting in more of the Manganese Dioxide reacting with the Hydrogen peroxide hence increasing the speed of the reaction. And a smaller surface area will have a slower reaction rate compared to a larger surface area.
- Concentration of the Hydrogen Peroxide - A high concentration of Hydrogen Peroxide would speed up the rate of decomposition. This because the concentration has an affect on how strong the Hydrogen Peroxide is. The higher the concentration the stronger the Hydrogen Peroxide is likely to be. So if the Hydrogen Peroxide has a stronger concentration that will mean that it is very reactive. Therefore being reactive means it will react faster and speed up the reaction.
- The use of a catalyst – There are two types of catalysts. They are biological catalysts and chemical catalysts. An example of a chemical catalyst is manganese Dioxide. A few examples of biological catalysts are carrots, potatoes and Liver. Catalysts are used to speed up reactions. Biological catalysts contain enzymes that break down certain substances in to other, easier to break down substances. The enzyme amylase, found in the saliva, breaks down starch into maltose. A disadvantage of using biological catalysts is that they rely on certain temperatures to ensure that they work best. Enzymes in your body work best at 37 degrees centigrade, which is your actual body temperature.
When Manganese Dioxide is added to Hydrogen Peroxide, the Hydrogen Peroxide is begins to break down in to two substances. Hydrogen Peroxide breaks down in to Oxygen and water. To collect data I cannot measure the amount of water produced. This is because it will be very difficult to separate the water produced as it has been dissolved with the hydrogen peroxide.
Instead I am going to measure the volume of Oxygen in centimetres cube, as the Oxygen bubbles will not easily dissolve in water.
I am going to measure the oxygen by collecting the gas in a measuring
cylinder, which is full of water. The theory is that when the gas goes in to the
cylinder by a delivery tube, the oxygen gas pushes out the water. This process is called the downward displacement of water.
I have chosen to investigate how the concentration of Hydrogen Peroxide affects its decomposition.
Prediction
I think that if I increased the concentration of the Hydrogen Peroxide the
speed of the reaction will increase. I also think that as I increase the concentration of the Hydrogen Peroxide, more Oxygen will be produced.
This will happen because the higher the concentration the more easy it is for the Manganese Dioxide to react with the Hydrogen Peroxide. This because the concentration has an affect on how strong the Hydrogen Peroxide is. The higher the concentration the stronger the Hydrogen Peroxide is likely to be.
To make this investigation faster I could also add more of the Manganese Dioxide.
This will help make the investigation happen faster as there will be more of the Manganese Dioxide to react with the Hydrogen Peroxide.
A Catalyst is a compound that speeds up the rate of reaction without itself being consumed by the reaction. So when the manganese dioxide acting as the catalyst drops into the hydrogen peroxide, the faster rate of decomposition occurs.
Method
I am going to set up the apparatus as shown in the diagram and fill a conical flask with 10 cm3 of Hydrogen Peroxide and 40 cm3 of water, totalling up to 50 cm3. After two spatulas of Manganese Dioxide is added. As soon as the Manganese Dioxide is added the rubber bung is placed. This reaction is allowed to go on for 60 seconds. Then the volume of Oxygen produced will be measured and recorded in my results table.
This will be repeated the same way except for the Hydrogen Peroxide which is increased by 10 cm3 each time and decreasing the water by 10 cm3 each time.
The entire experiment is repeated 5more times and the results are recorded. Then an average result will found of the average volume of Oxygen.
Throughout both experiments I will keep the same equipment/ apparatus. I
will also keep the same amount of the catalyst, the Manganese Dioxide.
The time left for the reaction will also be kept the same as all the
reactions. The time allowed will be kept for 1 minute, after that. The
volume of the oxygen released by the reaction will be recorded.
Apparatus
Here is a list of all the equipment that I will be using to do the investigation:
• Clamp stand – Holding clamp that is holding the clamp.
• Clamp – Holding the Boss
• Conicle flask – Containing the Hydrogen Peroxide and Manganese Oxide
• Delivery tube – Carry the Oxygen from the Conical flask to the measuring cylinder
• Boss - Holding the measuring cylinder upright
• Measuring cylinder – To collect the Oxygen from the delivery tube
• Trough – To hold the water
• Stop clock – To record the time
Safety
- Throughout the reaction safety goggles w ill be worn at all times
- All the equipment / will be kept away from the table edge.
This is to prevent them from falling off me table top and shatter, causing
injury to anyone who is nearby, as they are made glass and could easily be
broken.
- As I am dealing with water I must do the investigation away from any
electricity sources because any spillage could lead to an electric shock. If
any water should be spilled on me floor, it should be mopped up
immediately so that nobody slips over the slippery surface, which may
cause fatal injury
This is what my results table will look like:
Results
Conclusion
From my results I have noticed that as I increase the concentration of the Hydrogen Peroxide, the more oxygen was produced. Looking at my line graph as it shows an increase of the volume of oxygen produced can prove this. If the investigation would be left for longer than one minute, the graph would eventually show the graph becoming steady meaning that the reaction is complete.
I have also noticed that when the reaction was taking place, the conical flask had become warm. This means that the reaction was an exothermic reaction. Exothermic means that heat was given off during the investigation.
The manganese dioxide speeds up the decomposition of hydrogen peroxide.
If I were to do this investigation again, I would change a few things like doing the experiment more than three times, as this would give better and accurate results.
I would use better ways to collect the oxygen, as sometimes the oxygen was lost whilst changing the measuring cylinder. This problem may have affected my results by giving me false impressions about the investigation.
