Photochemistry lab PDF

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Experiment 3

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Name: Recia Thomas

Partner: Sierra Cabrera

Student No: 20167977

Student No: 2016261

Lab Section: 033

Bench # (on computer screen): 44

Experiment 3. (1 week) (LPR) Photochemical Reaction with Ferrioxalate Purpos e 2 In this experiment, the properties of photosensitive chemicals will be explored by observing what colours of light are observed by the chemicals. Additionally, the way these chemicals will be observed through the creation of blue prints.

Introduction Photochemistry is used to explore and describe the chemical effects of light in a chemical reaction .1 For photochemistry to occur, light must be absorbed by a medium .3 If a specific wavelength of light can be absorbed by the medium being used, than the photon from the light is absorbed by the reactant and activates the chemical reaction .3 In this experiment, photochemistry will be used to determine how light effects ferrioxalate .2 To begin, ferric nitrate and oxalic acid are combined to create ferrioxalate, which is an ion that chemically reacts when exposed to light .2 When exposed to light, the ferrioxalate becomes unstable .2 Though a chemical reaction is happening when ferrioxalate is exposed to the light, there are no visible indicators .2 To be able to see how the light reacted with the ferrioxalate, potassium ferricyanide is added to change the color and intensity of the colour of ferrioxalate depending on how much each solution has reacted .2 The ferrioxalate and potassium ferricyanide react to produce a blue complex ion called Prussian blue .2 The blue complex ion is created when potassium ferricyanide displaces the oxalate and replaces it with its cyanide ions .2 The displaced oxalate and water in the solution create the blue complex ions that make the colour of the solution change .2

Procedure2 Part A: 1. Potassium ferrioxalate was prepared by weighing out 0.6g of Fe(N O 3 ¿ 3 dissolving it into 100 mL of RO water

∙ 9 H 2 O and

2. 0.4 g of oxalic acid was weighed out, added to the solution, mixed, and then stored away from light 3. The potassium ferricyanide solution was prepared by dissolving 1 g of potassium ferricyanide into 100 mL of water in an Erlenmeyer flask and mixed using a stirring bar 4. Six test tubes were labelled and filled with the ferrioxalate solution and stored away from light

Experiment 3

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Part B: 5. After each of the next steps, the test tubes were stored away from light again 6. One of the test tubes was left in the dark, one tube was exposed to white light for 5 seconds, the next tube was exposed to white light for 10 seconds, the next for 20 seconds, the next tube was exposed to red light for 10 seconds and the sixth test tube was placed in a boiling water bath for 1 minute 7. 20 drops of potassium ferricyanide solution was added to each of the test tubes Part C:

∙ 9 H 2 O to 25 mL 8. A new ferrioxalate solution was prepared by mixing 1 g of Fe(N O 3 ¿ 3 RO water and then 1g of oxalic acid was added and the solution was stored away from light 9. The ferrioxalate solution was poured into a petri dish and four white 9 cm circles were soaked in the solution in the dark to keep them unexposed 10. The papers were then dried in the vacuum filtration system while covered by a piece of cardboard 11. The papers were then placed under a light with objects over them for several minutes 12. The objects were removed, and the papers were soaked in petri dishes of the potassium ferricyanide solution and then rinsed using water and allowed to dry 13. The lab space and the equipment were cleaned

Observations Test Tube 1 2 3 4 5 6

Exposure None White light for 5 seconds White light 10 seconds White light for 20 seconds Red light for 10 seconds Boiling water for 1 minute

Colour Light green/ yellow Green/blue Darker green/blue Dark turquoise Green/ blue – similar to 2 Green

Part A: -

1.009 g of potassium ferricyanide measured out

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0.6 g of ferrioxalate measured out

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0.43g of oxalic acid measured out

Part B: -

Ferrioxalate solution looks yellow before adding potassium ferricyanide

Part C: -

1.0 g of oxalic acid was measured

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1.01 g of ferrioxalate was measured

Experiment 3

Questions 1. During the trials involving the test tubes and floodlights, one test tube was not irradiated, some were irradiated with white light, and one was irradiated only with red light. Which trial showed the most amount of reaction? Which showed the least? Explain your results in terms of the absorption of light by ferrioxalate. The test tube that was exposed to white light the longest, test tube #4, or the test tube that was boiled (which also was exposed to light for one minute while boiling) showed the most amount of reaction because they were the test tubes that were the most developed when the potassium ferricyanide was added and showed the darkest colour. The least reacted test tube was the test tube that was kept out of the light and this is because it had no photons to activate the reaction that potassium ferricyanide was added to emphasize. The least reactive light was the red light because the test tube that went under red light was under light for 10 seconds and only showed the same results as the test tube that was exposed to white light for 5 seconds. This means that the red light took twice as long as the white light to get the same absorption results. This shows that the wavelength of the red light is not as well received as the white light is. Therefore, in general, the more exposure to light, the greater the reaction. 2. Why did you rinse the finished blueprints with water? What would happen if you did not do that? The blueprints are rinsed with water to get the residual chemicals on the paper off. This is so that the colour does not keep developing as the blueprints are exposed to light. If the chemicals were not rinsed off, the image made would not be as clear as the colour would continue to develop and ruin the details of the blueprint.

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Experiment 3

Pictures

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Experiment 3

References 1. Photochemistry. (2019, October 3). Retrieved November 15, 2019, from https://en.wikipedia.org/wiki/Photochemistry. 2. Queen’s Chemistry First-Year Laboratory Manual Chemistry 112 3. Smith, K. C. (2014, March 18). Retrieved November 15, 2019, from http://photobiology.info/Photochem.html

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