Chemistry

Exponential Decay of a Transition Metal Complex Ion

Exponential Decay of a Transition Metal Complex Ion Discussion Plots: Absorbance vs. Concentration Absorbance Concentration (mg/L) 5mL 0.032 25 10mL
0.065
2.50
15mL
0.097
3.75
Solution A
0.131
5.00
Standard Curve for Absorbance vs. Concentration
Figure 1
We got the standard curve equation.
By using this equation, we can determine the iron concentration for each absorbance measured during the decomposition runs.
For 25°C at 0 min.
Concentration vs. Absorbance at different Temperature
25°C
35°C
45°C
time (min)
Abs.
Conc.
ln(conc.)
Abs.
Conc.
ln(conc.)
Abs.
Conc.
ln(conc.)
0
0.107
4.106
1.413
0.104
3.992
1.384
0.097
3.726
1.315
10
0.102
3.916
1.365
0.089
3.422
1.230
0.040
1.559
0.444
20
0.099
3.802
1.336
0.079
3.041
1.112
0.017
0.684
-0.379
30
0.095
3.650
1.295
0.068
2.624
0.965
0.007
0.304
-1.190
40
0.090
3.460
1.241
0.061
2.357
0.858
0.004
0.190
-1.660
50
0.086
3.308
1.196
0.053
2.053
0.719
0.001
0.0760
-2.576
60
0.081
3.118
1.137
0.046
1.787
0.581
0.000
0.0380
-3.270
Plot the Iron Concentration versus Time
Figure 2
Plot the Natural Log of Iron Concentration versus Time
Calculation:
ln [Fe (phen)3++] = (-kt )+ ln [Fe (phen)3++]o
slope= -k → k= -(slope)
For 25⁰c
Slope=-0.0045
k=0.0045
Half life=
Run 1 (45°C)
Run 2 (35°C)
Run 3 (25°C)
Slope of Graph of Ln[Fe] vs. time
-0.0753
-0.0132
-0.0045
Value of k
0.0753
0.0132
0.0045
Half Life, minutes
9.203
52.5
154
DISCUSSION
1. How is the rate of decay of a transition metal complex ion affected by the temperature?
In Measured of the rate of decay of radium at room temperature and after being cooled in liquid hydrogen. We conclude that the decay rate was entirely independent of temperature. Since then, numerous investigations have shown that alpha and beta decays are not influenced by external conditions such as temperature, air pressure, or the surrounding material.
High temperatures increase the rate of collision and thus speeding up the rate of decay in transition elements. At normal temperatures microorganisms are able to survive and thus speeding up the reaction rate.
It has shown that the rate of alpha, beta, and electron capture decays all depend on temperature and whether they are placed in an insulating or a conducting material. Thats exciting because it raises the possibility of treating radioactive waste products. But it also raises a problem for particle physicists whose entire standard model assumes that decay rates cannot be influenced by external factors.
2) How is the half life affected by the temperature and how does this contrast with the effect of temperature on nuclear decay reactions? Please discuss your answer.
Radioactive half life is a measure of a nucleus propensity to spontaneously split. Fundamental force – weak nuclear
Temperature at the microscopic level is the kinetic energy of an atom – fundamental force – electric and electromagnetic
Temperature affects a completely different kind of radiation that has nothing to do with half life.
Let’s say we have a radioactive element X in a closed environment, if we were to measure the half-life of element Xs radioactive decay at:
1) Near absolute zero
2) At room temperature
3) At 1000s of degrees Kelvin
the results show that temperature does not affect in any way the half life of a substance.
The two are unrelated, so no there is no relationship between the two properties. I dont think temperature has anything to do with the nucleonic states, only the kinetic energy of the electrons in a solid. So temperature should have no effect on half life. In fact, temperature and chemical changes have no effect on the decay of nuclides. The only way to change the half life is to move it at relativistic speeds and then it becomes a matter of which reference frame you measure it in. In fact for the frame at rest with the nuclide there is no change in half life at relativistic speeds.

Reference:
Peter Atkins and Julio de Paula, Atkins Physical Chemistry, 8th edn (W.H. Freeman 2006
Meitner L, Frisch OR (1939) Disintegration of uranium by neutrons: a new type of nuclear reaction Nature
Chemical kinetics of solids By Hermann schmalzried

Back To Top