To Observe the Effect of Temperature on the Rate of the Iodine Clock Reaction Using Ammonium Persulfate

Topics: Chemical reaction, Chemical kinetics, Iodine Pages: 4 (665 words) Published: August 26, 2013
Aim: To observe the effect of temperature on the rate of the iodine clock reaction using ammonium persulfate

Assessment criteria: Design


Table 1.1: List of dependent and independent variables.
S.No| Dependent variables| Independent variables| Controlled variables| 1.| Rate of reaction| Temperature| Concentration|
2.| -| -| Pressure| 3. | -| -| Volume|


The iodine clock reaction is an experiment that demonstrates chemical kinetics in action. The iodine clock reaction exists in several variations; this particular experiment is conducted according to the Persulfate variation.

Two colorless solutions are to be mixed; though there is no visible reaction initially. Shortly thereafter, the liquid suddenly turns to a shade of dark blue. This clock reaction uses ammonium persulfate to oxidize iodide ions to iodine.

2I- (aq) + S2O82- (aq) → I2 (aq) + 2SO42- (aq)

Subsequently, sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color.

I2 (aq) + 2S2O32- (aq) → 2I- (aq) + S4O62- (aq)

An important factor that affects the rate of reaction is temperature. Temperature is proportional to the average kinetic energy, which is the energy associated with motion. All reactions have energy equivalent to the activation energy of the reaction. When we increase the temperature of a reaction, the average kinetic energy of the reactants increase. This change results in two things.

Firstly, there is an increase in the amount of collisions. Secondly, more molecules now have an energy equal to the activation energy and can now form products. More collisions, more energy, and a greater probability of favorable collisions leads to an increase in reaction rate. Again, the opposite is true if we decrease the temperature.

Apparatus required:

55 ml...
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