Rate of Reaction

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Science Investigation (Chemistry) – Rate of Reaction

Planning:

Outline: I will investigate the relationship between the rate of a reaction and the amount of catalyst added to the reaction. I will use hydrogen peroxide and speed pu the decomposition of it by adding manganese(IV), MnO2 as catalyst.

Fair test:

In order to maintain fair test conditions I will control variables that will affect the rate of reaction.

The factors that are able to affect the rate of reaction include:

  • Temperature
  • Surface Area
  • Concentration
  • Catalyst

Since I am investigating the relationship between rate of reaction and catalysts, the other 3 factors will remain constant throughout the experiment.

Temperature: At higher temperatures, the faster moving particles have more kinetic energy. This means they are moving quicker and will collide more often and with more energy, causing an increase in the number of effective collisions.

Surface Area: If more surface area is available, the number of particles of the solid reactant available for collision will increase. However, I am dealing with hydrogen peroxide (liquid) then there isn’t a surface area for me to control.

Concentration: More concentrated solutions contain more particles in the same space, making them more likely to collide. The increase in the number of collisions with sufficient energy increases the rate of reaction.

These explain why I would need to control those factors because they would affect my results dramatically. I will keep them constant:

Temperature: room temperature, temperature of hydrogen peroxide (17.C)

Surface area: n/a

Concentration: 5 volumes (halved the maximum which is 10 volumes, ratio 1:1)

However, for room temperature, I will do all experiments in the same room hopefully the temperature remains constant in that one room.

Safety:

Whilst this experiment is relatively safe, there are still safety considerations that must be adhered to:

  • Due to the dangerous nature of many of the compounds involved in this experiment, it is important that safety goggles or safety glasses are worn during all tests.
  • It is equally important to avoid skin contact with the compounds, as some are irritants. This can be done by ensuring that a suitable method is followed precisely so that there are no unexpected events that would lead to skin contact.

Accuracy and Reliability:

I will take 3 measurements of oxygen produced at each reading I will take. I will then use the arithmetic mean of these measurements in my analysis to calculate average rate of reaction. This should help to minimize unreliable results. Whilst I am doing my experiment, I will note the results down on a table, in order to spot any obvious anomalies.

The measurements themselves will be taken as carefully as possible. Time will be measured using the stop-watch (precise to ±0.1 second), volume of gas produced with the gas syringe (precise to ±1 cm³), the mass of the powdered manganese oxide with measuring balance (precise to ±0.01g) and the volume of hydrogen peroxide with a measuring cylinder (precise to ±0.5ml)

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Prediction:

I predict that the grater the amount of manganese oxide, MnO2, is added to the solution, the greater the rate of reaction – decomposition.

The formula for this decomposition is:

H2O2 (aq) => 2H2O (l) + O2 (g)

Hydrogen peroxide => Water + Oxygen

The manganese dioxide is present to be acted as a catalyst and as with all catalysts would lower the activation energy required in order for this reaction to take place. In doing so, the rate of reaction will be increased. Since more catalyst is present, it means there are more surface area of the catalyst so ...

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