In this experiment, the rate of decomposition is calculated by measuring the volume of the product gas using water displacement. The reactant used is household bleach, which contains 5 to 6% of NaClO. The decomposition can be stated in this following equation:
2 ClO- (aq) –> 2 Cl- (aq) + O2 (g)
To measure the rate of decomposition, a catalyst is needed to fasten the reaction. A suitable catalyst is Co2O3, which is produced from mixing Co(NO3)2 and bleach. The reaction can be described as follows:
2 Co2+ (aq) + ClO- (aq) + 2H2O (l) –> Co2O3 (s) + 4 H+(aq) + Cl-(aq)
Purpose
The objective of this experiment is to determine the rate of decomposition of bleach by measurement of gas production at several different temperatures.
Hypothesis
The decomposition rate will increase if the surrounding temperature increases. If the surrounding temperature increases by 10C, the reaction rate will double. If the temperature decreases by 10C, then the reaction rate will decrease by half.
Materials
* Household Bleach
* Co(NO3)2 solution
* Erlenmeyer flask
* Stopper and tube
* Ring stand
* Burette
* Graduated cylinder
* Thermometer
* Burette clamp
Procedure
Refer to lab instruction sheet – “Decomposition of Bleach”
Data
Table 1 – Accumulation of Oxygen at Room Temperature (24C)
Time Interval (s)
Volume of Gas (mL)
Time Interval (s)
Volume of Gas (mL)
30
3.5
210
29.9
60
9.1
240
34.3
90
13.4
270
38.3
120
18.0
300
42.0
150
20.8
330
44.5
180
25.9
360
50.1
Table 2 – Accumulation of Oxygen at 10C above Room Temperature (34C)
Time Interval (s)
Volume of Gas (mL)
Time Interval (s)
Volume of Gas (mL)
30
8.1
180
37.5
60
13.9
210
41.3
90
20.4
240
45.4
120
26.0
270
49.4
150
31.8
\
Table 3 – Accumulation of Oxygen at 10C below Room Temperature (14C)
Time Interval (s)
Volume of Gas (mL)
Time Interval (s)
Volume of Gas (mL)
60
0
900
27.2
120
0
960
29.5
180
0
1020
31.9
240
1.8
1080
33.5
300
4.0
1140
36.0
360
6.5
1200
38.0
420
8.9
1260
40.5
540
11.8
1320
42.1
600
13.2
1380
44.1
660
15.6
1440
45.6
720
18.1
1500
47.5
780
21.0
1560
49.6
840
23.0
1579
50.0
Analysis
Calculations:
Reaction rate at room temperature = = 0.14 mL O2 / s
Reaction rate at 10C above room temperature = = 0.17 mL O2 / s
Reaction rate at 10C below room temperature = = 0.036 mL O2 / s
Table 4 – Rate of Decomposition of Bleach
Surrounding Temperature (C)
Reaction Rate (mL/ s)
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