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Factors Affecting the Equilibrium Reaction of Iron (III) and Thiocyanate ions

argumentative Essay
2713 words
2713 words
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Factors Affecting the Equilibrium Reaction of Iron (III) and Thiocyanate ions

Research Question

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 quantitative data of the absorbance of the solution will allow the determination of the concentration of the Iron (III) Thiocyanatoiron using the Beer–Lambert Law. The difference in concentration of the solution per temperature point provides the precise effect of temperature on the reaction’s equilibrium position.

Introduction

This experiment investigates how changing a factor that affects the equilibrium reaction, in this case temperature, affects the equilibrium position.

Fe 3+ (aq) + S︎CN – (aq) ⇌ Fe ( SCN ) 2+ (aq) ( ∆H = - ve )

Pale Yellow Colorless Blood Red

This experiment uses Iron (III) ion and thiocyanate ion; the two chemicals are yellow colored and colorless, respectively. The product of the forward reaction is Iron (III) Thiocyanatoiron, which has a blood red color.

Dynamic equilibrium is when the macroscopic properties of the reaction are in constant at a specific temperature when the rate of the forward reaction is equal to that of the reverse reaction in a closed system. (Derry, Connor & Jordan, 2009)

Le Chatelier's Principle states that the change in temperature, pressure, or concentration will cause a shift in the reversible. (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.

In this essay, the author

  • Explains how the change in temperature of iron (iii) thiocyanatoiron affects the absorbance of the solution.
  • Compares the iron (iii) thiocyanatoiron (aq) in various temperatures using a digital water bath.
  • Analyzes the production rate of thiocynate ion measured by the degree of change in color using a colorimeter after 600 seconds since the reactants are mixed.
  • Explains that the absorbance of the solution will determine the concentration of iron (iii) thiocyanatoiron using the beer–lambert law. the difference in concentration provides the precise effect of temperature on the reaction’s equilibrium position.
  • Analyzes the temperature of the iron (iii) thiocyanatoiron solution containing iron ions and thiophenate ion (aq) at 25 °c, 30, 35, 40, 45, 50, 55, and 60 degrees celsius.
  • Analyzes the light absorbance of iron (iii) cyanatoiron (measured using the shimadzu uvmini-1240 uv-vis spectrophotometer) in order to determine the equilibrium concentration.
  • Explains that different spectrophotometers have slight differences in operating mechanism; the difference may cause unbalanced data collection, causing deviation in results.
  • Recommends turning on the shimadzu uvmini-1240 uv-vis spectrophotometer and letting it heat up for 15 minutes.
  • Explains how to transfer 1 cm3 blanking solution (distilled deionized water) to the 1cm3 square es quartz cuvette.
  • Recommends rinsing the cuvette using distilled deionized water for three times.
  • Explains drying the cuvette by inverting the apparatus up side down on a sheet of laboratory tissue.
  • Extracts 4.0 g of iron (iii) nitrate crystal to a 10 cm3 beaker, measured by the electronic balance.
  • Explains how to fill the 10 cm3 beaker with distilled deionized water until it reaches the 10-cm3 mark.
  • Explains how to turn on the hot plate without turning the heat component on.
  • Explains how to drop the magnetic stirrer into the 10 cm3 beaker containing the iron (iii) nitrate and distilled deionized water.
  • Explains how to remove the magnetic stirrer from the beaker using a magnet.
  • Adds additional distilled water to the conical flask, until the solution reaches a volume of 100 cm3.
  • Explains how to repeat stage 21 to 30 with 1.6 g of potassium thiocyanate.
  • Explains that after the iron (iii) nitrate and potassium thiocyanate are transferred into separate 250 cm3 conical flasks, label the conically containing alpha; and bravo.
  • Explains how to extract 10 cm3 solution from alpha using a volumetric pipette.
  • Explains how to extract 10 cm3 solution from bravo using another volumetric pipette into the other 20cm3 test tube.
  • Recommends placing a digital thermometer into the water bath to monitor the temperature of the digital bath.
  • Explains that if the temperature concurs to 25 °c, proceed to the next step.
  • Explains how to position the test tubes rack vertically into the water bath, with the solutions beneath the surface.
  • Explains how to position thermometers into both test tubes to confirm if the temperature of the solution is at 25 °c.
  • Explains mixing the solution from charlie into delta and starting the stopwatch simultaneously.
  • Recommends allowing the new solution in test tube delta to react for 10 minutes (600 seconds) in order for the equilibrium to occur.
  • Explains how to position the constant temperature cell holder by connecting it with the spectrophotometer’s cuvette receptacle.
  • Recommends extracting 1 cm3 of solution using a volumetric pipette from test tube delta into the square es quartz cuvette.
  • Advises to inset the cuvette into the receptacle with the clear sides facing left and right if the wavelength is set correctly.
  • Explains that the uvmini-1240 uv-vis spectrophotometer will automatically determine the absorbance of the solution and display it on the screen.
  • Explains how to record the absorbance value of the solution shown on the machine display screen into a spreadsheet document.
  • Recommends rinsing the cuvette three times with distilled deionized water.
  • Explains drying the cuvette by inverting the apparatus up side down on a sheet of laboratory tissue.
  • Recommends repeating stages 33 to 57 with unused test tubes. after 5 trials at the same temperature, proceed to stage 54.
  • Repeats stage 33 to 58 with unused test tubes. increase the temperature of the water bath and the constant temperature cell holder by 5°c each time.
  • Explains that after 10 trials, the iron (iii) nitrate and potassium thiocyanate solutions in the 250 cm3 conical flask made in stage 32 would be used up.
  • Explains derry et al. (2009) chemistry for use with the ib diploma programme standard level.
  • Explains precision cells' method of calibrating a spectrometer using nsg spectrophotometer calibration standards.
  • Explains that the experiment investigates how changing a factor that affects the equilibrium reaction, in this case temperature, impacts the balance position.
  • Explains that the beer–lambert law of light absorption provides a great insight to this phenomenon.
  • Explains that temperature should be controlled within the trial, as it is one of the factors affecting the equilibrium reaction. the digital water bath provides a temperature-monitored environment for the reactants and the solution.
  • Explains that chemical concentration should be controlled, as it is one of the factors affecting the equilibrium reaction. inconstant concentration of chemicals could change the final solution’s concentration.
  • Explains that the volume of the solution in the cuvette should always be controlled at 1.00 cm3 in order to maintain the same concentration for all trials.
  • Explains how the shimadzu uvmini-1240 uv-vis spectrophotometer allows experiment conductors to set the apparatus to produce light at a specific wavelength for all trials.
  • Explains that different electronic balances have slight discrepancies in terms of their precision to specific mass, increasing apparatus uncertainty in the experiment.
  • Explains that the size of the cuvette affects the results generated by the spectrophotometer. other variables ( & l) must be kept constant, as the only changing variable is a, solution absorbance.
  • Explains that a fixed time for each trial allows the reaction to reach equilibrium before the spectrophotometry stage.
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