Factors Affecting the Equilibrium Reaction of Iron (III) and Thiocyanate ions. (Revise)
How does the change in temperature of Iron (III) Thiocyanatoiron, containing iron (III) ions Fe3+ (aq) and thiocyanate ions SCN¬¬- (aq), affect the absorbance of the solution?
- Temperature at 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, and 60 °C (equilibrate the Iron (III) Thiocyanatoiron (aq) in various temperatures using a digital water bath, and temperature checked using a digital thermometer connected to a data logger)
- Production rate of thiocynate ion measured by the degree of change in color using a colorimeter after 600 seconds since the reactants are mixed.
- The ...view middle of the document...
(Derry, Connor & Jordan, 2009) Temperature, pressure, and concentration of a chemical are factors that may cause a shift in equilibrium position; the shift is to compensate the changes made by one of the three factors.
Since the forward reaction is exothermic, the increase in temperature increases the rate of the reversed reaction, meaning more Fe 3+ (aq) and S︎CN – (aq) will be formed, thus shifting the equilibrium position to the left, so the solution will be in yellow. On the other hand, the decrease in temperature increases the rate of the forward reaction, as more Fe ( SCN ) 2+ complex is produced, shifting the equilibrium position to the right, so the solution will be in red.
The Beer–Lambert Law of light absorption provides a great insight to this phenomenon. According to Davidson College (2014), the equation of Beer–Lambert Law is A = ε l c. A is the solution absorbance; ε is the molar absorptivity; l is the path length; c is the solution concentration. ε and l are to be kept constant throughout the experiment and A is collected using a spectrophotometer. By having information about the solution absorbance, molar absorptivity and path length, the solution concentration can be calculated. The collective data gained from the solution absorbance value from all trials conducted at different temperature level can show the change in solution concentration is affected by temperature.
In order to measure the equilibrium...