Chemistry Experiment Booklet PDF

Chemistry Experiment Booklet R. Gallagher Experiment: Page: R. Gallagher www.theconicalflask.ie Flame tests...

Chemistry Experiment Booklet R. Gallagher Experiment: Page: R. Gallagher www.theconicalflask.ie Flame tests 3 Anions tests 4 To measure the molecular mass of a volatile liquid 8 To prepare a standard solution of sodium carbonate 9 To use a standard solution of sodium carbonate to standardise a given hydrochloric acid solution 10 To prepare a solution of sodium hydroxide and standardise it with a standard hydrochloric acid 11 solution to prepare sodium chloride To determine the concentration of ethanoic acid in vinegar 12 To determine the amount of water of crystallisation in hydrated sodium carbonate (washing soda) 13 To prepare a standard solution of ammonium iron(II) sulfate and to use this solution to 14 standardise a solution of potassium permanganate by titration To determine the amount of iron in an iron tablet 15 To prepare a solution of sodium thiosulfate and to standardise it by titration against a solution of 16 iodine To determine the percentage (w/v) of sodium hypochlorite in household bleach 17 To monitor the rate of production of oxygen from hydrogen peroxide using manganese dioxide 18 (catalyst) To study the effect of temperature on the reaction rate using sodium thiosulfate and hydrochloric 19 acid To study the effect of concentration on the reaction rate using sodium thiosulfate and 20 hydrochloric acid To illustrate Le Chateliers principle using the reaction between iron(III)chloride and potassium 21 thiocyanate To determine the total water hardness in a water sample using EDTA 23 To determine (i) the total suspended solids and (ii) the total dissolved solids in a sample of water 24 To measure the amount of dissolved oxygen in a sample of water by means of a redox titration 25 To estimate the concentration of free chlorine in a swimming pool using a colorimeter 26 To prepare ethene and examine its properties 27 To prepare ethyne and examine its properties 28 To determine the heat of reaction of hydrochloric acid with sodium hydroxide 29 To extract clove oil from cloves by steam distillation and isolate eugenol 30 To prepare a sample of soap 31 To study the reaction of ethanal with a acidified potassium permanganate 32 To study the reaction of ethanoic acid with sodium carbonate 34 To oxidise phenylmethanol to benzoic acid with potassium permanganate under alkaline 35 2 conditions & recrystallise a sample to measure the melting point To separate the components of ink using paper chromatography 37 R. Gallagher www.theconicalflask.ie To carry out flame tests with different salts Method: 1. Soak a wooden splint in some water. 2. Dip the damp wooden splint into the salt. 3. Hold the splint over a flame and observe colour. Results: Salt: Colour observed: Lithium Crimson Potassium Lilac Barium Green Strontium Red Copper Blue-green Sodium Yellow Conclusion: Each metal provides a unique colour due to the different electron configurations of the elements and therefore different electron transitions of energy levels. 3 R. Gallagher www.theconicalflask.ie Anion tests 🤢 To test for the presence of chloride ions Method: 1. Dissolve any sodium salt in deionised water - clear solution. 2. Add a few drops of silver nitrate solution 3. Note the precipitation formed (AgCl) 4. Add ammonia solution to confirm presence of silver chloride 5. Note the disappearance of the precipitate. Results: Colour change: Clear to white precipitate formed. Ag+ + Cl- AgCl Precipitate disappears once ammonia solution added. Conclusion: Chloride ions are present in solution. 4 R. Gallagher www.theconicalflask.ie To test for the presence of sulphate and sulphite ions Method: 1. Dissolve any sulphate and sulphite salts in deionised water in different test tubes. - clear solution formed in both. 2. Add a barium chloride solution to both - white precipitate forms in both solutions. Ba2+ + SO42- BaSO4 Ba2+ + SO32- BaSO3 3. Add dilute hydrochloric acid to both solutions and note the differences in solubility between the sulphate and sulphite. Results: Sulphate: Cloudy precipitate remains due to barium sulphate being insoluble in HCl. BaSO4 + HCl No reaction Sulphite: Cloudy precipitate disappears due to it being soluble in HCl. BaSO3 + HCl BaCl2 + SO2 + H2O Conclusion: Both a sulphate and a sulphite can be detected using barium chloride. The sulphate and sulphite can be identified by then adding HCl and observing the differences in solubility. 5 R. Gallagher www.theconicalflask.ie To test for the presence of carbonate and hydrogen carbonate ions Method: 1. Dissolve any carbonate and hydrogen carbonate salt in deionised water in different test tubes. 2. Add a hydrochloric acid to both - effervescence occurs in both solutions. Bubble through limewater to show its carbon dioxide gas produced. 3. Add magnesium sulphate to both solutions and note the differences in precipitation between the carbonate and hydrogen carbonate salts. Results: Carbonate: Cloudy precipitate forms due to insoluble magnesium carbonate formed. Mg2+ + CO22- MgCO3 (Insoluble) Hydrogen carbonate: Cloudy precipitate doesn’t form due to soluble magnesium hydrogen carbonate formed. Mg2+ + 2HCO3- Mg(HCO3)2 (soluble) Conclusion: Both carbonate and hydrogen carbonate can be detected using HCl. The carbonate and hydrogen carbonate can be identified by then adding MgSO4 and observing the differences in solubility. Additional equations: CO22- + 2H+ CO2 + H2O HCO3- + 2H+ CO2 + H2O 6 R. Gallagher www.theconicalflask.ie To test for the presence of nitrate ions Method: 1. Dissolve any nitrate salt in deionised water. 2. Add fresh iron(II) sulfate solution to test tube. 3. Add concentrated sulphuric acid slowly down the side of test-tube using a dropper. 4. Note the formation of a brown ring at the junction of the liquids. Results: A brown ring at the junction of the liquids. Conclusion: Nitrate ions (NO3-) are present. To test for the presence of phosphate ions Method: 1. Dissolve any phosphate salt in deionised water. 2. Add ammonium molybdate solution to test tube. 3. Add concentrated nitric acid slowly down the side of test-tube using a dropper. 4. Place the test-tube in warm water. Results: A yellow precipitate is formed. Conclusion: Phosphate ions are present. 7 R. Gallagher www.theconicalflask.ie To measure the relative molecular mass of a volatile liquid Method: 1. Get the mass of a clean, dry conical flask including the tinfoil and rubber band. 2. Get the volume of the conical flask by filling it entirely with water and pouring it into a graduated cylinder. 3. Place propanone into the conical flask and put the tin foil with rubber band around the top of conical flask. 4. Put a pin hole in tin foil to ensure pressure inside conical flask is the same outside conical flask, i.e. obtained using a barometer. 5. Place conical flask in a water bath and heat until liquid has vaporised - use a thermometer to determine temperature. 6. Remove flask from water bath and dry. Allow to cool 7. Reweigh the conical flask and get the difference - this is the mass of the volatile liquid. 8. Calculate mr. Results: Mr = Mass/no. moles Use PV = nRT to calculate no.moles Sample calculations can be seen on www.theconocalflask.ie Important: Units are very important here. P = Pascals V = m3 n = no. moles R = 8.3 (universal gas constant) T = Kelvin 8 R. Gallagher www.theconicalflask.ie To prepare a standard solution of sodium carbonate Method: 1. A known mass of sodium carbonate is measured on a clock glass and mass balance. 2. The mass is then added to a clean/dry beaker. 3. A wash bottle (deionised water) is used to wash all traces of the sodium carbonate into the beaker. 4. A small volume of deionised water is added to dissolve the sodium carbonate. 5. A clean glass rod is used to stir the solution to ensure powder dissolves completely. 6. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 7. A wash bottle (deionised water) is used to wash all traces of the sodium carbonate into the volumetric flask. 8. The volumetric flask is filled to the calibration mark and read at eye level and filled up to the bottom of the meniscus. A dropper is used to ensure accuracy. 9. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 9 R. Gallagher www.theconicalflask.ie To use the standard solution of sodium carbonate to standardise a given hydrochloric acid solution Method: 1. Pipette is rinsed with deionised water and then sodium carbonate. 2. Pipette 25mL of sodium carbonate into clean conical flask. 3. Burette is rinsed with deionised water and then HCl. 4. Clamp burette vertically. 5. Fill burette so that bottom of meniscus is on the mark when read at eye level. 6. Place white tile underneath conical flask - see colour change better. 7. Add 3 drops methyl orange. 8. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 9. Stop titration once first permanent faint pink colour is observed. 10.First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: Na2CO3 + 2HCl 2NaCl + H2O + CO2 Colour change: Orange to faint pink Sample calculations are on the www.theconicalflask.ie 10 R. Gallagher www.theconicalflask.ie To prepare a solution of sodium hydroxide and standardise it with a standard hydrochloric acid solution to prepare sodium chloride Method: 1. A known mass of sodium hydroxide is measured on a clock glass and mass balance. 2. The mass is added to a clean/dry beaker. 3. A wash bottle (deionised water) is used to wash all traces of the sodium hydroxide into the beaker. 4. A small volume of deionised water is added to dissolve the sodium hydroxide. 5. A clean glass rod is used to stir the solution to ensure solid dissolves completely. 6. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 7. A wash bottle (deionised water) is used to wash all traces of the sodium hydroxide into the volumetric flask. 8. The volumetric flask is filled to the calibration mark. 9. The calibration mark is read at eye level and filled up to the bottom of the meniscus. 10. A dropper is used to ensure accuracy. 11. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 12. Pipette is rinsed with deionised water and then sodium hydroxide. 13. Pipette 25mL of sodium hydroxide into clean conical flask. 14. Burette is rinsed with deionised water and then HCl. 15. Clamp burette vertically. 16. Fill burette so that bottom of meniscus is on the mark when read at eye level. 17. Place white tile underneath conical flask - see colour change better. 18. Add 3 drops methyl orange. 19. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 20. Stop titration once first permanent faint pink colour is observed. 21. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. 22. Pour a small sample of the solution into an evaporating dish. Evaporate the solution and note the presence of white crystals - sodium chloride. Results: NaOH + HCl NaCl + H2O Colour change: Orange to faint pink Sample calculations are on the www.theconicalflask.ie 11 R. Gallagher www.theconicalflask.ie To determine the concentration of ethanoic acid in vinegar Method: 1. Rinse pipette with deionised water and then vinegar solution. 2. Pipette vinegar to a volumetric flask and add water to dilute. Dilution is necessary to prevent excess amounts of sodium hydroxide being used. 3. The volumetric flask is filled to the calibration mark. 4. The calibration mark is read at eye level and filled up to the bottom of the meniscus. A dropper is used to ensure accuracy. 5. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 6. Pipette is rinsed with deionised water and then sodium hydroxide. 7. Pipette 25mL of sodium hydroxide into clean conical flask. 8. Burette is rinsed with deionised water and then the diluted vinegar. 9. Clamp burette vertically. 10. Fill burette so that bottom of meniscus is on the mark when read at eye level. 11. Place white tile underneath conical flask - see colour change better. 12. Add 3 drops phenolphthalein. 13. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 14. Stop titration once pink colour goes colourless. 15. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: CH3COOH + NaOH CH3COONa + H2O Sample calculations on www.theconicalflask.ie 12 R. Gallagher www.theconicalflask.ie To determine the amount of water of crystallisation in hydrated sodium carbonate (washing soda) Method: 1. A known mass of sodium carbonate crystals is measured on a clock glass and mass balance. 2. The mass is then added to a clean/dry beaker. 3. A wash bottle (deionised water) is used to wash all traces of the sodium carbonate into the beaker. 4. A small volume of deionised water is added to dissolve the sodium carbonate. 5. A clean glass rod is used to stir the solution to ensure crystals dissolves completely. 6. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 7. A wash bottle (deionised water) is used to wash all traces of the sodium carbonate into the volumetric flask. 8. The volumetric flask is filled to the calibration mark. 9. The calibration mark is read at eye level and filled up to the bottom of the meniscus. 10. A dropper is used to ensure accuracy. 11. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 12. Pipette is rinsed with deionised water and then sodium carbonate. 13. Pipette 25mL of sodium carbonate into clean conical flask. 14. Burette is rinsed with deionised water and then HCl. 15. Clamp burette vertically. 16. Fill burette so that bottom of meniscus is on the mark when read at eye level. 17. Place white tile underneath conical flask - see colour change better. 18. Add 3 drops methyl orange. 19. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 20. Stop titration once first permanent faint pink colour is observed. 21. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: Na2CO3 + 2HCl 2NaCl + H2O + CO2 Sample calculations can be seen on www.theconicalflask.ie 13 R. Gallagher www.theconicalflask.ie To prepare a standard solution of ammonium iron(II) sulfate and to use this solution to standardise a solution of potassium permanganate by titration Method: 1. A known mass of ammonium iron(II) sulfate crystals is measured on a clock glass and mass balance. 2. The mass is then added to a clean/dry beaker. 3. A wash bottle (deionised water) is used to wash all traces of the ammonium iron(II) sulfate into the beaker. 4. A small volume of deionised water is added to dissolve the ammonium iron(II) sulfate. 5. A clean glass rod is used to stir the solution to ensure crystals dissolves completely. 6. Sulfuric acid was added to the beaker to prevent ammonium iron(II) sulfate being oxidised from Fe2+ to Fe3+ ions by oxygen in air. 7. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 8. A wash bottle (deionised water) is used to wash all traces of the ammonium iron(II) sulfate into the volumetric flask. 9. The volumetric flask is filled to the calibration mark. 10. The calibration mark is read at eye level and filled up to the bottom of the meniscus. 11. A dropper is used to ensure accuracy. 12. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 13. Pipette is rinsed with deionised water and then ammonium iron(II) sulfate. 14. Pipette 25mL of ammonium iron(II) sulfate into clean conical flask. 15. Add more sulfuric acid to ensure enough H+ ions to reduce MnO4- completely. 16. Burette is rinsed with deionised water and then KMnO4. 17. Clamp burette vertically. 18. Fill burette so that top of meniscus is on the mark when read at eye level. 19. Place white tile underneath conical flask - see colour change better. 20. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 21. Stop titration once first permanent faint pink colour is observed. 22. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: MnO4- + 8H+ + 5Fe2+ Mn2+ + 4H2O Sample calculations can be seen on www.theconicalflask.ie 14 R. Gallagher www.theconicalflask.ie To determine the amount of iron in an iron tablet Method: 1. A known mass of 5 iron tablets is measured on a clock glass and mass balance. 2. The tablets are crushed with a mortar and pestle. 3. A wash bottle (deionised water) is used to wash all traces of the tablets into a beaker of sulfuric acid. 4. Sulfuric acid was added to the beaker to prevent ammonium iron(II) sulfate being oxidised from Fe2+ to Fe3+ ions by oxygen in air. 5. A clean glass rod is used to stir the solution to ensure tablets dissolves completely. 6. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 7. A wash bottle (deionised water) is used to wash all traces of the tablets into the volumetric flask. 8. The volumetric flask is filled to the calibration mark. 9. The calibration mark is read at eye level and filled up to the bottom of the meniscus. 10. A dropper is used to ensure accuracy. 11. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 12. Pipette is rinsed with deionised water and then the iron tablet solution. 13. Pipette 25mL of the solution into clean conical flask. 14. Add excess sulfuric acid to ensure enough H+ ions to reduce MnO4- completely. 15. Burette is rinsed with deionised water and then KMnO4. 16. Clamp burette vertically. 17. Fill burette so that top of meniscus is on the mark when read at eye level. 18. Place white tile underneath conical flask - see colour change better. 19. Titrate, ensuring that the conical flask is swirled and the sides are washed with a little deionised water. 20. Stop titration once first permanent faint pink colour is observed. 21. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: MnO4- + 8H+ + 5Fe2+ Mn2+ + 4H2O Sample calculations can be seen on www.theconicalflask.ie 15 R. Gallagher www.theconicalflask.ie To prepare a solution of sodium thiosulfate and to standardise it by titration against a solution of iodine Method: 1. A known mass of sodium thiosulfate crystals is measured on a clock glass and mass balance. 2. The mass is then added to a clean/dry beaker. 3. A wash bottle (deionised water) is used to wash all traces of the sodium thiosulfate into the beaker. 4. A small volume of deionised water is added to dissolve the sodium thiosulfate. 5. A clean glass rod is used to stir the solution to ensure crystals dissolves completely. 6. The solution is added to a 250 mL clean/dry volumetric flask using a funnel slowly to avoid splashing and loss of solution. 7. A wash bottle (deionised water) is used to wash all traces of the sodium thiosulfate into the volumetric flask. 8. The volumetric flask is filled to the calibration mark and read at eye level and filled up to the bottom of the meniscus. A dropper is used to ensure accuracy. 9. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 10. Clamp burette vertically and rinse with deionised water and then sodium thiosulfate. 11. Fill burette so that bottom of meniscus is on the mark when read at eye level. 12. Pipette KMnO4 into clean conical flask. 13. Add sulfuric acid to ensure enough H+ ions to reduce MnO4- completely. 14. Add excess potassium iodide (KI) to ensure all potassium permanganate has reacted (reduced) and to keep the iodine produced in solution. 15. Place white tile underneath conical flask - see colour change better. 16. Titrate, swirl conical flask and wash the sides with a little deionised water. 17. Pause titration once first permanent faint yellow colour is observed. 18. Add starch indicator and continue to titrate until solution goes colourless. 19. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: 2MnO4- + 16H+ + 10I- 2Mn2+ + 5I2 + 8H2O I2 + 2S4O32- S4O6 + 2I- Colour changes in the conical flask: 1. Purple to reddish-brown (addition of potassium iodide) 2. Reddish brown to straw yellow (addition of sodium thiosulfate) 3. Straw yellow to blue black (addition of starch indicator) 4. Blue black to colourless (addition of sodium thiosulfate) Sample calculations can be seen on www.theconicalflask.ie 16 R. Gallagher www.theconicalflask.ie To determine the percentage (w/v) of sodium hypochlorite in household bleach Method: 1. Rinse pipette with deionised water and then bleach solution. 2. Pipette bleach to a volumetric flask and add water to dilute. Dilution is necessary to prevent excess amounts of sodium thiosulfate being used. 3. The volumetric flask is filled to the calibration mark. 4. The calibration mark is read at eye level and filled up to the bottom of the meniscus. A dropper is used to ensure accuracy. 5. The volumetric flask is stoppered and inverted 20 times to mix thoroughly. 6. Pipette is rinsed with deionised water and then bleach solution. 7. Pipette 25mL of diluted bleach into clean conical flask. 8. Burette is rinsed with deionised water and then the sodium thiosulfate solution. 9. Clamp burette vertically and rinse with deionised water and then sodium thiosulfate. 10. Fill burette so that bottom of meniscus is on the mark when read at eye level. 11. Add sulfuric acid to ensure enough H+ ions to reduce ClO- completely. 12. Add excess potassium iodide (KI) to ensure all bleach has reacted (reduced) and to keep the iodine produced in solution. 13. Place white tile underneath conical flask - see colour change better. 14. Titrate, swirl conical flask and wash the sides with a little deionised water. 15. Pause titration once first permanent faint yellow colour is observed. 16. Add starch indicator and continue to titrate until solution goes colourless. 17. First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: ClO- + 2H+ + 2I- Cl- + I2 + H2O I2 + 2S4O32- S4O6 + 2I- Colour changes in the conical flask: 1. Colourless to reddish-brown (addition of potassium iodide) 2. Reddish brown to straw yellow (addition of sodium thiosulfate) 3. Straw yellow to blue black (addition of starch indicator) 4. Blue black to colourless (addition of sodium thiosulfate) Sample calculations can be seen on www.theconicalflask.ie 17 R. Gallagher www.theconicalflask.ie To monitor the rate of production of oxygen from hydrogen peroxide using manganese dioxide (catalyst) Method: 1. Place hydrogen peroxide solution into the conical flask. 2. Place a small vial containing manganese dioxide - black powder (catalyst) in the conical flask upright. 3. Attach conical flask to delivery tube connected to inverted graduated cylinder in a water trough. 4. Knock the vial and start timer immediately. 5. Bubbling occurs - oxygen gas being produced. 6. Record the volume of oxygen gas produced every 30 seconds. 7. Table and graph the results. Results: Initially there was a sharp increase in rate however the rate soon slowed and ceased eventually when the hydrogen peroxide had fully decomposed. See sample calculations on ww.theconicalflask.ie 18 R. Gallagher www.theconicalflask.ie To study the effect of temperature on the reaction rate using sodium thiosulfate and hydrochloric acid Method: 1. A known concentration of sodium thiosulfate is poured into a conical flask. 2. The conical flask is placed over a white paper with an X marked on it. 3. A fixed amount of HCl is added and the timer started immediately. 4. The timer is stopped once the X is no longer visible. 5. The experiment is repeated with different temperatures of sodium thiosulfate using a hot plate. 6. The results are recorded and graphed. 7. Ensure the conical flask and apparatus are washed each time. Results: Na2S2O3 + 2HCl S + 2NaCl + SO2 + H2O As the temperature increased so did the rate of reaction. Conclusion: Rate of reaction is not directly proportional for temperature. 19 R. Gallagher www.theconicalflask.ie To study the effect of concentration on the reaction rate using sodium thiosulfate and hydrochloric acid Method: 1. A known concentration of sodium thiosulfate is poured into a conical flask. 2. The conical flask is placed over a white paper with an X marked on it. 3. A fixed amount of HCl is added and the timer started immediately. 4. The timer is stopped once the X is no longer visible. 5. The experiment is repeated with different concentrations of sodium thiosulfate. 6. The results are recorded and graphed. 7. Ensure the conical flask and apparatus are washed each time. Results: Na2S2O3 + 2HCl S + 2NaCl + SO2 + H2O As the concentration increased so did the rate of reaction. Conclusion: Rate of reaction is directly proportional to concentration. 20 R. Gallagher www.theconicalflask.ie To illustrate Le Chateliers principle using the reaction between iron(III)chloride and potassium thiocyanate (a) To show the effect of temperature on chemical equilibrium Method: 1. Add iron(III)chloride (FeCl3) to a test-tube with potassium thiocyanate (KCNS) 2. Observe the colour. 3. Heat the solution and note the colour change. 4. Cool the solution and note the colour change. FeCl3 + CNS- Fe(CNS)2+ + 3Cl- (negative delta H) Yellow Red Results: When heated the equilibrium shifts to the left hand side. When cooled the reaction shifts to the right hand side. Le Chatelier’s Principle: - States that if a stress is applied to a system at equilibrium, the system re-adjusts to relieve the stress applied. Endothermic: - Increase temperature drives reaction towards the products side. - Decrease temperature drives reaction towards the reactants side. Exothermic: - Increase temperature drives reaction towards the reactants side. - Decrease temperature drives reaction towards the products side. 21 R. Gallagher www.theconicalflask.ie (b) To show the effect of concentration on chemical equilibrium Method: 1. Add iron(III)chloride (FeCl3) to a test-tube with potassium thiocyanate (KCNS) 2. Observe the colour. 3. Add concentrated HCl to solution and note the colour change. FeCl3 + CNS- Fe(CNS)2+ + 3Cl- Yellow Red Results: When HCl added the equilibrium shifts to the left hand side due to the presence of the Cl- ions in the product side. Le Chatelier’s Principle: - States that if a stress is applied to a system at equilibrium, the system re-adjusts to relieve the stress applied. 22 R. Gallagher www.theconicalflask.ie To determine the total water hardness in a water sample using EDTA Method: 1. Pipette is rinsed with deionised water and then some of the hard water solution. 2. Hard water is pipetted into the conical flask. 3. Buffer 10 is added to the conical flask to ensure the edta does complex with the Mg2+ and Ca2+ ions. 4. Eriochrome black T is added to the conical flask to act as an indicator. The colour is wine red due to the presence of Mg2+ and Ca2+ ions. 5. Clamp burette vertically and rinse with deionised water and then some edta solution. 6. Fill burette so that bottom of meniscus is on the mark when read at eye level. 7. Place white tile underneath conical flask - see colour change better. 8. Titrate, swirl conical flask and wash the sides with a little deionised water. 9. Stop titration once blue colour is observed due to the Mg2+ and Ca2+ ions converting to edta complexes. Results: Colour change: Wine red to blue. H2X2- + Ca2+ CaX2- + 2H+ Edta ion Edta complex H2X2- + Mg2+ MgX2- + 2H+ Sample calculations on www.theconicalflask.ie 23 R. Gallagher www.theconicalflask.ie To determine (i) the total suspended solids and (ii) the total dissolved solids in a sample of water (i) To determine the total suspended solids Method: 1. Fill a volumetric flask to the mark with water. 2. Get the mass of filter paper. 3. Pour the water through the filter paper and funnel. 4. Dry filter paper and reweigh. 5. The difference is the mass of suspended solids. Results: The difference of masses of the filter paper indicates the mass of the suspended solids. Conclusion: The suspended solids can be determined by weight filter paper. (ii) To determine the total dissolved solids Method: 1. Get themes of a clean dry beaker. 2. Place a known volume of water into the beaker using a graduated cylinder. 3. Use a bunsen burner to evaporate the water off. 4. Reweigh the beaker once water evaporated. 5. The difference is the mass of dissolved solids. Results: The difference of masses of the beaker indicates the mass of the dissolved solids. Conclusion: The dissolved solids can be determined by evaporation of water. Note: g/L x 1000 = p.p.m. 24 R. Gallagher www.theconicalflask.ie To measure the amount of dissolved oxygen in a sample of water by means of a redox titration Method: 1. A bottle is rinsed with deionised water to remove impurities. 2. The bottle is then filled completely with a sample of water to be analysed - any air bubbles will result in an inaccurate titration. 3. Manganese(II)sulfate and alkaline potassium iodide solution are added by droppers submerged. They form a white precipitate that will react with dissolved oxygen. Submerging the dropper ensures the no air bubbles and loss of reagents. 4. A brown precipitate should form. 5. Concentrated sulfuric acid is added by submerging. The brown precipitate formed is replaced with a reddish brown solution (iodine liberated). 6. Pipette is rinsed with deionised water and then iodine solution. 7. Pipette solution into clean conical flask. 8. Burette is rinsed with deionised water and then sodium thiosulfate. 9. Clamp burette vertically. 10.Fill burette so that bottom of meniscus is on the mark when read at eye level. 11.Place white tile underneath conical flask - see colour change better. 12.Titrate, swirl conical flask and wash the sides with a little deionised water. 13.Pause titration once first permanent faint yellow colour is observed. 14.Add starch indicator and continue to titrate until solution goes colourless. 15.First titration is a rough titration. Perform two more titrations - ensuring the final two titrations are within 0.1mL of each other. Results: The concentration of dissolved oxygen is found by finding out the amount of iodine liberated by means of a ratio. Sample calculations are found on www.theconicalflask.ie 25 R. Gallagher www.theconicalflask.ie To estimate the concentration of free chlorine in a swimming pool using a colorimeter Method: 1. Five standard solutions of chlorine ranging from 1 - 5 ppm are made up. 2. A DPD tablet is added to each solution until dissolved. 3. A pink colour (free chlorine) is observed. 4. The solutions are placed in a colorimeter and the results recorded. 5. The colorimeter records absorbance. These are then graphed. Results: Results are plotted on a graph. Conclusion: The more free chlorine the greater the absorbance. Colorimeters can be used to detect lead, nitrates and phosphates in water. 26 R. Gallagher www.theconicalflask.ie To prepare ethene and examine its properties Al2O3 C2H5OH C2H4 + H2O Method: 1. Place some glass wool at the bottom of a test tube and put some ethanol onto the glass wool. Clamp test tube horizontal. The glass wool will hold the ethanol in place when horizontal. 2. Add some aluminium oxide to the test tube (centre). 3. Connect delivery tube to test tube and inverted test tubes in a water trough. 4. Place a bunsen underneath the aluminium oxide and heat. 5. Fill several test tubes of ethene. The first test tube will contain air and can be disposed. 6. Left the apparatus up out of water before turning off bunsen burner. This prevents ‘suck back’ occurring. 7. Test ethene test tubes to examine properties. Physical properties: Colourless and sweet smell. Combustion: When burned a bright luminous flame produced. C2H4 + 3O2 2CO2 + 2H2O Unsaturation: Presence of double or triple bond 1. Add acidified potassium permanganate: Purple to colourless 2. Add bromine water: Brown to colourless (Bromine water addition is an example of an addition reaction - mechanism) Ethene is used for ripening fruit. 27 R. Gallagher www.theconicalflask.ie To prepare ethyne and examine its properties CaC2 + 2H2O Ca(OH)2 + C2H2 Method: 1. Place calcium carbide in a bunker flask and attach a delivery tube to it. 2. Ensure acidified copper sulfate container is in between the calcium carbide and water trough. 3. Acidified copper sulfate captures the impurities (hydrogen sulfide, ammonia and phosphine) as ethyne is bubbled through it. 4. Calcium carbide forms bubbles (ethyne) when water reacts with it. The solution goes white because of calcium hydroxide forming. 5. Fill several test tubes of ethyne. The first test tube will contain air and can be disposed. 6. Test ethyne test tubes to examine properties. Physical properties: Colourless and sweet smell. Combustion: When burned a sooty flame produced. 2C2H2 + 5O2 4CO2 + 2H2O Unsaturation: Presence of double or triple bond 1. Add acidified potassium permanganate: Purple to colourless 2. Add bromine water: Brown to colourless Ethyne is used for welding and cutting. 28 R. Gallagher www.theconicalflask.ie To determine the heat of reaction of hydrochloric acid with sodium hydroxide HCl + NaOH NaCl + H2O Method: 1. Using a graduated cylinder place a known volume of HCl in a polystyrene cup. Polystyrene is a very good insulator. 2. Using a separate graduated cylinder place a known volume of sodium hydroxide into a separate polystyrene cup. Both solutions should be the same concentration. 3. Allow both cups to come to the same temperature. 4. Once the same temperature pour the NaOH to the HCl quickly and place lid on cup. A digital thermometer is used to record the temperature increase. 5. The cups are swirled (avoid splashing). Results: The heat rise was recorded and the heat of neutralisation calculated. Heat liberated (j) = Mass (g) x specific heat capacity x temp rise Note to improve accuracy: 1. Swirling ensures uniform mixing whereas splashing has an effect on temperature. 2. Digital thermometers are more accurate than alcohol thermometers. 3. A lid reduce heat loss to surroundings. 29 R. Gallagher www.theconicalflask.ie (a) To extract clove oil from cloves by steam distillation Method: 1. Set up the steam distillation apparatus. Apparatus functions: 1. Steam generator: a.k.a. copper kettle provides the steam. 2. Safety tube: For safety - to remove excess water. 3. Steam trap: To prevent excess steam entering the pear shaped flask. 4. Liebig condenser: To condensate the emulsion Results: A milky emulsion is collected. It is a mixture of clove oil and water. Note: Steam must be used opposed to heating the cloves directly as you would destroy the plant material (cloves) before extracting the oil. (b) To isolate clove oil (eugenol) from an emulsion of clove oil and water by liquid liquid extraction using cyclohexane Method: 1. Place the emulsion into a separating funnel and a small quantity of cyclohexane and shake. The cyclohexane will dissolve the clove oil (eugenol) without mixing with water. 2. The organic layer is on top. Collect both the organic and aqueous layer separately in beakers. 3. Place the aqueous layer back into the separating funnel and repeat steps 1-2. This is repeated a further two times to maximise the amount of eugenol collected from the emulsion. 4. Anhydrous magnesium sulfate (MgSO4) is added to the organic solution. MgSO4 removes any water present - it is a drying agent. 5. The mass of a clean dry conical flask is obtained and the solution is filtered to remove MgSO4 and water (hydrated magnesium sulfate). 6. Fresh cyclohexane is added to remove any traces of oil in the filter paper. 7. Place conical flask in water bath and heat, this will remove the cyclohexane as it is volatile. 8. The new mass is found and the difference is the mass of the clove oil. Sample calculations are on www.theconicalflask.ie 30 R. Gallagher www.theconicalflask.ie To prepare a sample of soap Method: 1. Set up a reflux apparatus. 2. Reflux for 30 mins to ensure completion and no loss of ethanol solvent. 3. Set up distillation apparatus to collect the ethanol. 4. The contents of the pear shaped flask is poured into a beaker containing brine. Brine (saturated NaCl) will precipitate the soap and dissolve any excess sodium hydroxide. 5. Use a small amount of water to ensure all washings go into the brine solution. 6. Soap (sodium stearate) is then filtered off and washed with ice cold water. Water removes any sodium hydroxide. It being ice cold prevents soaps dissolving too quickly. 7. The soap is allowed to air dry over night on filter paper. Reflux apparatus: - Oil: Glycerol tristerate is the key comment for making soap. - Sodium hydroxide: Soap making (base hydrolysis). - Anti dumping chips: Reduce the reaction vigour. - Ethanol: Solvent for the oil. Distillation apparatus: Liebig condenser: Condensates the ethanol. Result: The soap forms a lather in the presence of water. Glycerol tristearate + Sodium hydroxide Sodium stearate (soap) + Glycerol (propan 1,2,3- triol) 31 R. Gallagher www.theconicalflask.ie To study the reaction of ethanal with a acidified potassium permanganate Method: 1. Place ethanal and acidified potassium permanganate (oxidising agent) into a test tube. 2. Heat and observe colour change. Results: Colour change: Purple to colourless. Ethanal is being oxidised to ethanoic acid. Note: If you were to repeat this experiment with a ketone e.g. propanone there would be no colour change as ketones cannot be oxidised. Conclusion: Aldehydes can be oxidised to carboxylic acids but ketones cannot. To study the reaction of ethanal with Fehling’s reagent Method: 1. Make up Fehling’s reagent by adding Feelings A and Feelings B together. 2. Place ethanal and Fehling's (oxidising agent) into a test tube. 3. Heat and observe colour change. Results: Colour change: Royal blue to brick red Ethanal is being oxidised to ethanoic acid by Fehling’s reagent. Note: If you were to repeat this experiment with a ketone e.g. propanone there would be no colour change as ketones cannot be oxidised. Conclusion: Aldehydes can be oxidised to carboxylic acids but ketones cannot. 32 R. Gallagher www.theconicalflask.ie To study the reaction of ethanal with ammoniacal silver nitrate (silver mirror test) Method: 1. Add silver nitrate solution to sodium hydroxide and ammonia to make up a solution called Tollens’ reagent. 2. Place Tollens’ reagent in a clean dry test-tube and add ethanal. 3. Heat and observe colour change. Results: Colour change: Silver mirror forms on the inside of the test-tube. Ethanal is being oxidised to ethanoic acid by Tollens reagent. Note: If you were to repeat this experiment with a ketone e.g. propanone there would be no silver mirror forms as ketones cannot be oxidised. Conclusion: Aldehydes can be oxidised to carboxylic acids but ketones cannot. 33 R. Gallagher www.theconicalflask.ie To study the reaction of ethanoic acid with sodium carbonate 2CH3COOH + Na2CO3 2CH3COONa + CO2 + H2O Method: 1. Place anhydrous sodium carbonate and ethanoic acid into a boiling tube connected to a solution of limewater. 2. Observe. Results: Bubbling occurs. Limewater going milky shows this gas is carbon dioxide. To study the reaction of ethanoic acid with magnesium metal 2CH3COOH + Mg (CH3COO)2Mg + H2 Method: 1. Place magnesium metal into a solution of ethanoic acid. 2. Place a lighted taper above the mouth of the test-tube and observe the ‘pop’ produced. Results: Hydrogen gas is produced. To study the reaction of ethanoic acid with ethanol Method: 1. Add ethanol and ethanoic acid together with some sulfuric acid (catalyst). 2. Observe the results Results: Colour change: None Fruity smell is produced due to ethyl ethanoate (ester) formed. 34 R. Gallagher www.theconicalflask.ie (a) To oxidise phenylmethanol to benzoic acid with potassium permanganate under alkaline conditions Method: 1. Place phenylmethanol, potassium permanganate (oxidising agent) and sodium carbonate (reaction works best in alkaline conditions) into a conical flask. Purple colour. 2. Heat the conical flask in a water bath for 20 mins. Brown precipitate formed. 3. Cool the flask and add concentrated hydrochloric acid. Use blue litmus paper to ensure acidic conditions. - HCl functions: 1. Convert sodium benzoate to benzoic acid. 2. Neutralises any excess sodium carbonate 3. Acidic medium enables Mn4+ ions into Mn2+ ions. 4. Add sodium sulfite to reduce Mn4+ ions into Mn2+ ions. White crystals formed. 5. Place conical flask in ice to crash out the crystals. 6. The crystals are filtered off using a Buckner flask and funnel. 7. Crystals are allowed to air dry over night. Results: Colour changes are due to oxidation state changes: Purple Brown white crystals KMnO4 MnO2 Mn2+ +7 +4 +2 35 R. Gallagher www.theconicalflask.ie (b) To recrystallise a sample of benzoic acid Method: 1. A known mass of benzoic acid crystals are dissolved in the minimum amount of hot water. Must be hot as benzoic acid is very soluble in hot water. The more solvent - the less crystals. 2. The solution is then filtered using a heated funnel. This removes any insoluble impurities. 3. The hot filtered solution is cooled in ice and begins to crystallise. Ice helps form large crystals to maximise yield. A seed crystal is added here to help speed up the process. 4. The crystals are collected by vacuum filtration. Soluble impurities do not form crystals are are separated from the crystals during this stage. 5. The crystals are allowed air dry and their mass is obtained. (c) To measure the boiling point of benzoic acid Method: 1. A capillary tube end is melted (sealed) using a bunsen burner. 2. The benzoic acid crystals are crushed using a pestle and mortar. 3. They are then placed in the capillary tube and placed into a melting point block. 4. The temperature range of them melting is recorded. Result: Melting point range 121-122℃ High melting point with a narrow range indicates high purity. 36 R. Gallagher www.theconicalflask.ie To separate the components of ink using paper chromatography Method: 1. Place an ink drop on the chromatography paper. 2. Place paper into the gas jar with a solvent that does not go above the ink drop. 3. Observe the colour components separating as solvent moves up the paper. Results: The colour comments separate out showing ink is a mixture made out of several colours. Stationary phase: chromatography paper. Mobile phase: Solvent 37