Data collection and processing:
Table 1. The volume of O2 (ml) using MnO2 as a catalyst
Table 2. The volume of O2 (ml) using liver as a catalyst
The uncertainties of a mass of catalyst are +-0.05 g and the uncertainties of the volume of O2 are +-0.1 ml, the uncertainties of time are +-0.1 s.
Below the results obtained are represented graphically:
Rate of reaction = increase in concentration of product ∕ time
2H2O2 (l) 2H2O(l) + O2(g)
C (H2O2 ) = 1 mol dm-3
V (H2O2 ) = 10 ml = 0.01 dm-3
n (H2O2 ) = C*V = 1* 0.01 = 0.01 mol
From the reaction above we see that from 2 moles of hydrogen peroxide 1 mole of oxygen is obtained, thus from 0.01 mol of hydrogen peroxide, 0.01∕2 = 0.005 mol of oxygen is obtained.
Now, the increase in concentration of O2 and the rate of reaction after 10 s are calculated:
n (O2) = 0.005 mol
V (O2) = 3.6 ml = 0.0036 dm-3
C = n∕V = 0.005∕0.0036 = 1.39 mol dm-3
Rate of reaction = 1.39∕10 = 0.139 mol dm-3 s-1
Total uncertainties:
V (H2O2 ) = 0.0005/0.01*100 = 5%
V (O2) = 0.0001/0.0036*100 = 2.8%
Time (s) = 0.1/10*100 = 1%
Total percentage uncertainties = 5 + 2.8 + 1 = 8.8%
8.8% of 0.139 mol dm-3 s-1 is 0.012232 mol dm-3 s-1
The tables below represent the rates of reaction at different time intervals for different amounts of chemical catalyst MnO2 and biological catalyst liver.
Table 3. The rate of reaction (mol dm-3 s-1 ) using MnO2 as a catalyst
Table 4. The rate of reaction (mol dm-3 s-1 ) using liver as a catalyst
Uncertainties:
6.0% of 0.016 mol dm-3 s-1 is 0.00096 mol dm-3 s-1
5.7% of 0.007 mol dm-3 s-1 is 0.000399 mol dm-3 s-1
5.6% of 0.004 mol dm-3 s-1 is 0.000224 mol dm-3 s-1
5.5% of 0.003 mol dm-3 s-1 is 0.000165 mol dm-3 s-1
5.4% of 0.002 mol dm-3 s-1 is 0.000108 mol dm-3 s-1
5.4% of 0.002 mol dm-3 s-1 is 0.000108 mol dm-3 s-1
5.3% of 0.001 mol dm-3 s-1 is 0.000053 mol dm-3 s-1
11.0% of 0.250 mol dm-3 s-1 is 0.0275 mol dm-3 s-1
7.8% of 0.050 mol dm-3 s-1 is 0.0039 mol dm-3 s-1
6.7% of 0.023 mol dm-3 s-1 is 0.001675 mol dm-3 s-1
6.3% of 0.013 mol dm-3 s-1 is 0.000819 mol dm-3 s-1
6.0% of 0.008 mol dm-3 s-1 is 0.00048 mol dm-3 s-1
5.9% of 0.006 mol dm-3 s-1 is 0.000354 mol dm-3 s-1
5.8% of 0.005 mol dm-3 s-1 is 0.00029 mol dm-3 s-1
5.7% of 0.004 mol dm-3 s-1 is 0.000228 mol dm-3 s-1
10.0% of 0.200 mol dm-3 s-1 is 0.02 mol dm-3 s-1
6.3% of 0.020 mol dm-3 s-1 is 0.0126 mol dm-3 s-1
5.9% of 0.010 mol dm-3 s-1 is 0.00059 mol dm-3 s-1
5.8% of 0.006 mol dm-3 s-1 is 0.000348 mol dm-3 s-1
5.7% of 0.005 mol dm-3 s-1 is 0.000285 mol dm-3 s-1
5.6% of 0.003 mol dm-3 s-1 is 0.000168 mol dm-3 s-1
5.5% of 0.003 mol dm-3 s-1 is 0.000165 mol dm-3 s-1
5.5% of 0.002 mol dm-3 s-1 is 0.00011 mol dm-3 s-1
8.9% of 0.143 mol dm-3 s-1 is 0.012727 mol dm-3 s-1
6.4% of 0.028 mol dm-3 s-1 is 0.0016 mol dm-3 s-1
6.0% of 0.013 mol dm-3 s-1 is 0.00078 mol dm-3 s-1
5.9% of 0.008 mol dm-3 s-1 is 0.000472 mol dm-3 s-1
5.8% of 0.006 mol dm-3 s-1 is 0.000348 mol dm-3 s-1
5.7% of 0.005 mol dm-3 s-1 is 0.000285 mol dm-3 s-1
5.7% of 0.004 mol dm-3 s-1 is 0.000228 mol dm-3 s-1
5.6% of 0.003 mol dm-3 s-1 is 0.000168 mol dm-3 s-1
Below is the graphical representation of the change in the reaction rates.
Conclusion and evaluation
The rate of reaction is the change in concentration per unit time. One of the factors that affect the reaction rate is the presence of catalyst: a substance which speeds up a chemical reaction and is left unchanged at the end of the reaction. Catalysts work by lowering the activation energy of a reaction which means that more particles have energy substantial enough to react and the reaction consequently happens faster.
In this work the effects of biological (liver) and chemical (MnO2) catalysts were investigated on the rate of reaction of decomposition of hydrogen peroxide. The hypothesis was that the greater amount of catalyst is used the faster the reaction will go to completion. As can be seen from the graphs 3 and 4 the reactions in the presence of the greatest mass of catalyst, i.e. 0.2 g of liver and MnO2 went to completion faster than in the presence of 0.1 g of catalysts. Thus, the hypothesis was verified.
Secondly, it was expected that chemical catalyst will be better than biological one. From the graphs it can be seen that though the reaction using the chemical catalyst really went to completion quicker, the difference was not a prominent one.
In the calculations it was obtained that that uncertainties affect the quantities of the substances, but are too small to interfere with the general trend for the particular reaction. Yet, if accurate results are needed, the fact that time, especially when dealing with such short intervals, can not be managed precisely and that the volume of O2 also can not be recorded at the particular moment really accurately, thus the results are approximations and not precise quantities.
Finally, to improve the experiment, the procedure should be repeated and more precise equipment could be used. Also, it would be an improvement to repeat experiment with more different catalysts to determine more accurately and evidently the differences in effects of biological and chemical catalysts.