lOMoARcPSD|16644971 Lost and Clueless The up-and-downs in the life of a (first year) university student. PAGES Home Chem 205 Laboratory Reports. Chem 205 Laboratory Reports. I now everybody is just looking for those. But be careful, don't copy, it's bad, not all my answers are right, it's for inspirationnal purposes only, and never, I repeat, never cite this website as a source for any information. Lab reports for Chem 205 (Concordia) Introductory Chemistry I. Chemistry 205 Experiment 1: Densities of Organic Liquids PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Laboratory Report Data and Observations Ethyl acetate Hexane Acetone Unknow n Mass of empty vial and cap (g) 12.583 11.719 11.856 12.431 Mass of vial, cap and liquid (g) 13.494 12.456 12.771 13.263 Mass of liquid (g) 0.911 0.737 0.915 0.832 Initial pipette reading (mL) 0 0 0 0 Final pipette reading (mL) -1.0 -1.0 -1.0 -1.0 Volume of liquid delivered 1.0 1.0 1.0 1.0 Does it dissolve in water? no no yes yes If not, does it sink or float? floats floats ø ø Calculation and Analysis 1. Densities of organic solvants Ethyl acetate Hexane Acetone Unknow n Calculated density (g/mL) 0.911 0.737 0.915 0.832 Accepted value (g/mL) 0.902 0.659 0.791 see below 9.98 11.7 15.7 see below Relative error ( % ) 1. The average relative errors of the densities is 12.36%. It is therefor impossible to identify the unknown liquid. The possibilities are: - tert-butyl methyl ether (0.741 g/mL, 12.2 % of relative error), ethanol ( 0.785 g/mL, 5.98 % of relative error), tert-butanol (0.786 g/mL, 5.85 % of relative error), PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 acetone (0.791 g/mL, 5.18 % of relative error), toluene ( 0.867 g/mL, 4.03 % of relative error), ethyl acetate (0.902 g/mL, 7.76 % of relative error). But, because the calculated densities gotten in this experiment procedure are over the accepted values, it cannot be toluene nor ethyl acetate. And since the melting point of tertbutanol is 25˚C , the only possibilities left are acetone, ethanol and tert-butyl methyl ether. All of which being soluble in water , there is no more information to tell them apart. 3.The relative error of the unknown liquid density is 5.18 % if it is acetone, 5.98 % if it is ethanol or 0.741 % if it is tert-butyl methyl ether. 4. Densities of ethyl acetate Run Density Experiment Absolute Deviation 1 0.911 g/mL 0.001 g/mL 2 0.886 g/mL 0.026 g/mL 3 0.886 g/mL 0.026 g/mL 4 0.906 g/mL 0.006 g/mL 5 1.01 g/mL 0.098 g/mL 6 0.875 g/mL 0.037 g/mL Averages 0.912 g/mL 0.032 g/mL 5. The average absolute deviation is 0.032 g/mL. This is a measure of how precise the measurements are. Meanwhile, the average error of my measurement is 9.98% This says how accurate I was compared to the accepted value. In order to improve the accuracy of the accepted value, the absolute deviation of a set of values is more useful than one single measure compared to the actual accepted value. That is, considering the value we have here, it is possible to consider 0.912 ± 0.032 g/mL as an accepted value, since it was calculated using six independent runs of a same procedure. To obtain the best possible value, different procedures have to be repeated over and over, each time minimizing errors until a set of values with a minimal average deviation is obtained. 6. Since the average value of set no. 1 is lower than the accepted value, this means that either the balance was registering masses too low, or the pipette was delivering a smaller volume than indicated. That is proved by the fact that if exactly 1 mL of water is weighted by the hypothetical balance, it would give a mass of lets say 0.97 g, therefor a density lower than the accepted value. And if the hypothetical pipette delivers instead of 1 mL, 0.97 mL, a perfectly zeroed balance reads 0.97 g, and the calculated density would be, again, smaller than the accepted value. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 7. The syringes are usually less precise than pipettes when it comes to measurement. This is why we use pipettes Chemistry 205 Experiment 2: Densities of Organic Liquids Prelaboratory Questions 1. a) Make the different acids (hydrochloric and acetic) react with a limiting amount of steel wool. Observe any changes in color, smell, etc. b) Observe the change in gas volume created by the reaction of acetic acid with steel wool, where acetic acid is the limiting reactant. (Place the wool in a test tube, add a few drops of acid, reverse the test tube in a beaker half-filled with water, note changes in water level) c) Make 4 mL of sodium carbonate and 1 mL of calcium chloride react together, observe changes in weight. Add sulfuric acid, observe further changes. (weight all the solutions and all the containers together before and after each reaction) 2. -Calcium chloride: CaCl₂ , solid. -Sodium carbonate: CaCO₃ , solid. -Sodium bicarbonate: Ca(CO₃)₂ , solid. -Carbon dioxide: CO₂ , gas. -The compound which, when dissolved in water, yields hydrochloric acid: HCl, gas. -The compound which, when dissolved in water, yields sulfuric acid: H₂SO₄ , liquid. 4.Observation: “The copper sheet [...] changes from the shiny pinkish color of pure copper to the familiar green color of old copper rooves.” Speculation: “The copper sheet [...] slowly reacts with water and carb on dioxide in the air [...].” Chemistry 205 Experiment 2: Making Scientific Observations Laboratory Report Objective: Differentiate ob servations, speculations and conclusions when ob serving reactions implying acids, b asses and metal. Observations and Data: PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 1. Action of hydrochloric acid on steel wool: Before reaction: The acid is a clear liquid, with a light vinegary smell. The steel wool is dull gray. During reaction: There are little gas b ub b les forming on the steel wool. After reaction: The acid still looks the same, it doesn’t smell as much. The steel seams a little b righter, b ut it can b e b ecause it is wet. Action of acetic acid on steel wool: Before reaction: The acid is a colorless, strongly smelling liquid. The steel wool is dull gray. During reaction: No ob servations. After reaction: Nothing changes. 1. Data for quantitative examination of action of acetic acid on steel wool: Length of the inside tube: 72 mm Inside diameter of the tube: 8 mm Volume of the test tube: 14476 mm² Initial reading of the level of water in the reaction tube: 0 mm Final reading of the level of water in the reaction tube: 10 mm Volume of level change: 2010 mm² Percentage change in the gas volume in the reaction tube: 14 % 1. Data for reaction involving sodium carbonate: Mass of empty glassware: 79.491 g Mass of beaker, Erlenmeyer and test tubes before reactions: 85.780g Observations upon adding the calcium chlorine solution: Formation of a white precipitate. The mixture looks more viscous. Mass of beaker, Erlenmeyer and test tubes after adding the calcium chlorine solution: 85.778 g Mass change: -0.002 g Observations upon adding the sulfuric acid: There is a violent reaction taking place, forming a lot of gas and a white powder. The mixture is very cloudy. Mass of beaker, Erlenmeyer and test tubes after adding the sulfuric acid: 85.694 g Mass change: -0.084 g PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 1. Procedure for disposal of the steel wool residues: a) Neutralize the acid b y slowly pouring sodium b icarb onate solution in the test tub e until it stops b ub b ling. b) Place a sheet of b rown paper in the sink, away from the drain c) Pour the solution in the sink, making sure any steel residue sicks on the paper. d) If the principal steel wool b all doesn’t fall b y itself, place the test tub e upside-down on the paper and gently tap it to dislodge the b all. e) Rinse the tub e with some water, repeat step c. Let water run for a few seconds. f) Dispose of the steel wool in the designated container, throw the paper in regular garb age. Conclusions and Interpretation of Results 1. Based on notes about strong and weak acids, it is possible to say HCl is a stronger acid than acetic acid. A strong acid is a substance that, when dissolved in water, separates into H⁺ and a anion. With the observations made, an easy speculate would be that strong acids reacts more with metals than weak acids. furthermore, this hypothesis becomes possible: the gas produced by the reaction with HCl is H₂; after a long period of time, Cl will create a deposit on the Fe as the concentration of hydrogen ions lower. 2. The gas volume in the test tube diminished, proving that a gas was used during the reaction, probably oxygen, to form an iron oxide. If HCl had been used, maybe the reaction would have been faster. 3. Unlike a cylinder, the test tube has a rounded bottom. This means that the volume of a test is smaller than the volume of the cylinder with corresponding dimensions. But, this error is only at the bottom. At the top, the tube opens up a little and sometimes, even has a tip, creating an irregular volume for the opening. When both those things are taken in consideration, our calculation has a net negative error. The real value is a larger number than the calculated one. 4. Based on the “Water Solubility of Ionic Compounds” table, the precipitate created upon addition of calcium chloride in the solution of sodium carbonate is calcium carbonate, because salts of carbonate are insoluble and calcium does not figure in the soluble compounds. At that stage, a small change of mass was noted. This means, somewhere in the reaction, a gas was produced. But, no bubbling was observed. When sulfuric acid is added, a possible reaction can be that one of the H⁺ from the acid creates a covalent bond with the carbonate ions, and has as product calcium bicarbonate. But, this hypothesis does not explain why there is a gas produces and a loss of mass. An explanation to that would be that in contact with some ion the solution, the hydrogen ions bonds together and gaseous hydrogen is formed. In the solubility table, we can see that calcium chloride is insoluble. This leads to an other possibility: after the addition of the sulfuric acid; hydrogen “steals” oxygen from carbonate, creating water and carbon dioxide. In this case, the second precipitate would be calcium sulfate. 5. “Matter can neither be created nor destroyed” (from week 4’s PowerPoint notes) The experiments conducted in the Erlenmeyer flask do not provide evidence of this law. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 There was a net diminution of mass from the reactants to the products. This ever goes against the law. But, we have evidence that a gas was produced. We can conclude that the difference of masses come from the fact the gas was not weighted alongside the other products after the reactions. But, this reaction is not a good evidence of the law of conservation of matter since it if not happening in a closed system. Chemistry 205 Experiment 3: Separation of a mixture Prelaboratory Questions 1. Procedure: a. Remove the iron filings 1.Place the mixture in a weighing dish. Note the mass. 2.Using a magnet, get all the iron on one side of the dish. Do not put the magnet in the mixture, work through the dish. 3.Pour out the mixture in a flask, holding the iron back with the magnet. Note the mass. a. Recuperate naphthalene 1.Fill in a test tube with ice, fit the adapter on it. Place the test tube in the flask. 2.Put the flask, with it’s side-arm open, in a 75-80˚C water bath. Fit a pipette bulb on the side-arm of the flask 3.Change melted ice for frozen one in the test tube regularly. 4.When all the naphthalene is securely crystalized, remove the test tube, scrape off the crystals and weight them. a. Separate the solids 1.Weight the flask, add water to the solution. 2.Connect everything like in the picture in the manual. 3.Pour out the liquid though the filter. Start step d with urea solution. 4. Place the filtrate in a beaker, add water to particles left in the flask, pour it all in the beaker. Let the sand sink and the plastic float. Separate. a. Crystalize urea 1.Place a stopper on the flask, using the water aspirator, make sure air flows. 2. Slowly heat up solution without letting it bubble. 2. Urea is the only substance of the mixture that is dissolved in water, because it it the only one one that is left when we get to the point of evaporating the solvent. 3. Since urea is a polar molecule (it dissolved in water) and naphthalene is not (since it PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 was not dissolved), any non-polar solvent would dissolve naphthalene, like hexane or dichloromethane but urea would stay in the water. Then, by decantation and evaporation, both solutes can be be extracted and isolated. 4. a.Moth balls tend to sublimate when left in an open area for long. b.Naphthalene can be detected using smell. c.That is a result of its volatility. 5. Iron is the only element in the mixture: naphthalene and urea are compounds, sand and polypropylene are themselves mixtures. This said, there might be trace of a pure element in the sand. 1. Sand is likely to contain: gemstones, metals, rocks, granite, shell fragments, etc. In terms of chemical elements, we will find: sulfur, oxygen, carbon, hydrogen, iron, copper, nickel, silver, etc. Chemistry 205 Experiment 3: Separation of a mixture Laboratory Report Objective Separate components of a mixture using their physical properties. Procedure 1. Weight approximately 1 g of the mixture in a weighting dish. 1.1 Re-zero the the balance before each measurement 1.2 Note the mass of the dish 1.3 Pour some of the mixture in the dish. 1.4 Weight and add or remove until the balance read “mass of the dish + ~1 g” 1.5 Calculate the exact of mixture used. 1. Separate the iron from the mixture 2.1 In the weighting dish, push all the mixture to one side 2.2 Place the side of the u-shaped magnet on the bottom of the dish, near the edge of the heap of mixture. 2.3 Slowly drag the magnet to the opposite side of the dish. 2.4 Repeat the two previous steps until most of the iron is separated from the mixture. Use a scoopula to scrape the mixture back in the heap as needed. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 2.5 Scoop the iron into a weighted flask. 2.6 Repeat this process until all of the iron has been dragged out of the mix. 1. Separate the naphthalene from the mixture 3.1 Pour the rest of the mixture in an erlenmeyer flask. 3.2 Prepare the apparatus found at page 3 - 21 of the lab manual 3.3 When the water temperature reaches 75˚C, turn down the heat and put on the side bulb. 3.4 Make naphthalene condensate 3.4.1 Use the pipette to draw out melted ice. Add more ice as needed. 3.4.2 Wipe the water of the rubber stopper 3.6 Keep repeating step 3.4 until all the naphthalene has solidly crystalized on the cold test tube. 3.7 Take out the assemblage but keep the water bath. 3.8 Scrape off the naphthalene in a weighted flask 1. Separate urea 4.1 Prepare the appropriated filtration apparatus as found on page 3 - 22w 4.2 Pour out the solution that is now found in the flask from previous step on the filter. Water comes from condensation 4.3 Place the flask with the filtrated urea solution in the water bath. Connect to the water aspirator. Turn the aspirator on. 4.4 Wait for the water to evaporate, do steps 5 and 6. 4.5 In this case, water did not evaporate. Discard remaining solution in the sink at the end of the experiment. 1. Separate the polypropylene 5.1 Add water to the sand and polypropylene mix. Pour it all in a small beaker 5.2 Let it rest for a while. 5.3 Using the filtrations apparatus, pour only about half of the water, the polypropylene should all fall on the filter paper. 5.4 Scrape any remaining polypropylene from the side of the beaker. 5.5 Let the filter paper dry. Transfer the polymer in a weighted flask. 1. Dry sand 6.1 Carefully pour out any supernatant water. 6.2 Place the beaker on the hot plate until sand is dry. 6.3 Transfer the sand in a weighted flask. Data and Observations PRO version Mass of mixture used 1.123 g Mass of iron recovered 0.730 g Percent in mixture 65.0% Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Mass of naphthalene recovered 0.001 g Percent in mixture 0.09% Mass of urea recovered 0g Percent in mixture 0% Mass of polypropylene recovered Percent in mixture 0.053 g 4.7% Mass of sand recovered 0.196 g Percent in mixture 17.4% Total mass of material recovered 0.980 g Total percent recovery 87.3% The principal difficulties encountered during the procedure were: -When trying to separate the iron from the rest, particles are dragged the metal. This part must then be repeated a number of times. -During that, naphthalene keeps sublimating and is lost. -For the set of naphthalene sublimation, water kept condensation on the rubber stopper and it slipped into the erlenmeyer flask, which get the mixture wet and later, made it impossible to transfer out of the flask into a beaker. -When trying to isolate urea, time became a problem as water evaporated too slowly and urea was never recuperated. -For the steps toward the separation of the polypropylene from sand, many problems arose. Fist, once on the filter paper, it was almost impossible to get the particles of it without scraping little pieces of paper along. -Then, for decantation, some sand appeared to be floating, with the polypropylene instead of sinking as expected. This might be explained by the fact that, with there very small masses, sand particles can be supported by the force of the water membrane like the one that allows water spiders to stay afloat. Additional Questions 1. Yes, the order in which the separation was performed was important. some steps could have been interchanged, but not all. For example, naphthalene could have, and should have been sublimated first. But, urea couldn’t have been separated first, because the polypropylene would have melted at water’s boiling temperature. 2. If iron was replaced with magnesium, another method of separation should have been PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 found because magnesium is a non-magnetic metal. On the other hand, nickel reacts just like iron in contact of magnets, which means the method would have worked anyways with nickel instead of iron. 3. Gold has a highest density then sand, so when the pan in swirled, sand will raise higher on the sides because of centrifugal forces than gives a body an acceleration inversely proportional to its mass. Chemistry 205 Experiment 4a: Preparation of Lead(II) Iodide Prelaboratory Questions 1.-Transfer 7.0 mL of potassium iodide solution and 2.0 mL of lead(II) nitrate solution in a beaker using a graduated transfer pipette and a volumetric pipette respectively. Note observations before, during and after the reaction. -Prepare and weight a filter paper. Place the paper in a funnel and the funnel in an erlenmeyer flask. -Pour the solution and the suspended solid on the filter paper, making sure as much solid as possible is poured out. Rinse any remaining precipitate with the filtrate. Filter again. Discard the filtrate. -Rinse the filter paper with 2 mL of pure water. Note the appearance of the solid. Discard the filtrate. -Repeat this last step using acetone. -Let the filter paper and the solid dry in a beaker under the fume hood for about half an hour. -When everything is dry, weight the paper and lead(II) iodine. Note the mass of the solid. Try transferring the solid in a weighted watch glass. Calculate the mass of solid. Discard the product 2. Pb²⁺ (aq) + 2 NO₃⁻ (aq) + 2 K⁺ (aq) + 2 I⁻ (aq) Pb²⁺ (aq) + 2 I⁻ (aq) PbI₂ (s) PbI₂ (s) + 2 K⁺ (aq) + 2 NO₃⁻(aq) 3.The limiting reactant lead(II) nitrate, because only 2 mL is used agains 7 mL of the other reactant while both have the same molarity and the molar proportion is 1:2, not 2:7. This means 1/7 of the potassium iodide will not react.The theoretical yield of the experiment is therefor of 88.8% ( (7+2-1) mol / (7+2) mol ) Chemistry 205 Experiment 4b: Synthesis of manganese(II) chloride Prelaboratory Questions PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 1. -Weight about 0.05 to 0.1 g of manganese in a carefully weighted beaker. Note mass. -Add about 1.5 mL of hydrochloric acid to the metal using a Pasteur pipette and working under a fume-hood. Wait for 5 minutes. Note any change in temperature. -Dry the content of the beaker by heating it on a hot plate. Note its appearance. -Let the beaker cool in the desiccator. Weight it. -Reheat the beaker for 3-5 minutes. Repeat previous step. Do this until two consecutive values have less then 0.003 g between them. Note the mass. -Dissolve the manganese(II) chloride in water, dispose in provided container. 2. The molar mass of pure solid iron is: 55.85 g/mol. This means 0.05 g represents 8.95255 x 10-4 moles. The molar mass of FeCl2 is: 126.74 g/mol. This means 0.145 g represents 1.14407 x10-3 moles. The molar mass of FeCl3 is: 162.20 g/mol. This means 0.145 g represents 8.93958 x 10-4 moles. Since this reaction has a ratio of 1 mole of product per mol of iron, the chloride of iron obtained was FeCl3, ferric chloride. 3. If the yield in the experiment had been less then 100 percent, n, the number of Cl per molecule would had have to be higher, because the molar mass would have had to be greater to compensate the fact the number of moles was smaller for the same mass of products. Chemistry 205 Experiment 4: Preparation of Some Metal Halides Laboratory Report Objective Create lead(II) iodine and manganese(II) chloride using precipitation and redox reactions. Introduction A metal halide is a compound made of a metal and an element from the halogens, group VII A. Some are used in light bulbs to complete the radiation spectrum of mercury. The most common ways of creating metal halides are by precipitation of and insoluble halide or by reduction of the solid metal. A precipitation is a reaction is an aqueous solution were the cation from one reagents couples up with the anion from the other to form an insoluble product. They other ions are PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 called spectator ions and are found in the supernatant solution after the reaction. A redox occurs when once specie gains electrons that are lost by the other one in the reaction. It is in fact a couple of reaction: an oxidation, where electrons are lost and a reduction, where electrons are gained. The names comes from the fact oxygen is a common oxidizing agent. Redox reactions are often seen in solutions, but can also be the result of the interaction between a solid and a gas, amongst other. Procedure A. Preparation of lead(II) iodine 1. Mix the reagent solutions. 1.1Transfer 7.0 mL of potassium iodide solution from the stock bottle into a clean beaker using the dedicated 10 mL graduated transfer pipette. 1.2 Add 2.0 mL of lead(II) nitrate solution in a beaker using a volumetric pipette. 1.3 Swirl gently to mix. 1.4 Note observations before, during and after the reaction. 2. Filter the product. 2.1 Prepare and weight a filter paper. Place the paper in a funnel and the funnel in an erlenmeyer flask. 2.2 Keep the solid in suspension using the rubber policeman. 2.3 Pour the solution and the suspended solid on the filter paper. 2.4 Wipe the rubber policeman on the filter. 2.5 Rinse any remaining precipitate with the filtrate. 2.6 Repeat filtration process on the same filter until the beaker is clean. 1. Purify the precipitate 3.1 Rinse the filter paper with distilled water. 3.2 Note the appearance of the solid and the filtrate. 3.3 Rinse the filter paper with acetone. 3.4 Discard the filtrate in the container. 3.5 Let the filter dry. (Start part B of the experiment) 1. Isolate the product 4.1 Unfold the filter paper and place it on top of a beaker. 4.2 While waiting for product B to cool, hold the paper above the warm hot plate. 4.3 When the paper is dry and the powder starts to get loose, note mass 4.4 Carefully transfer PbI2 on the weighted glass watch. Note mass. 1.Weight about 0.05 to 0.1 g of manganese in a carefully weighted beaker. Note mass. 1.1 Note mass of empty beaker 1.2 Add some manganese 1.3 Adjust volume until the mass falls in the required bracket. 1. Add hydrochloric acid 2.1 Work under a fume hood. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 2.2 Using the provided bottle, add 30 drops of HCl 2.3 Let everything react for 5 minutes. Note observations. 3. Isolate the product 3.1 Dry the content of the beaker by heating it on a hot plate. 3.2 Note its appearance. 3.3 Let the beaker cool in the desiccooler. Weight it. 3.5 Reheat the beaker for 5 minutes. 3.6 Repeat steps 3.3 and 3.4 two times, finish by cooling 3.7 Note the mass. Discard of products: -Put the filter and the PbI2 in the designated container. -Dissolve the manganese(II) chloride in water, dispose in provided container. Observations A. Addition of lead(II) nitrate to potassium iodide in solution. -Reagent solutions are both clear. -When they are mixed, a bright yellow precipitate is formed. -The supernatant solution is cloudy. -The wet filtrated solid has the texture and look of paint pigments. -There is a silvery substance floating on the the solution/covering the precipitate. -After rinsing with water, the filtrate has a slight yellow color. A. Addition of HCl(aq) to manganese powder. -Sizzles, violent reaction. -Gas is produced. -Reaction is endothermic -Water condensates on the sides of the beaker. -Solution is dark-green. -When dry, a pinkish solid is left. Data and Calculation A. Data for the preparation of lead(II) iodide Volume of lead(II) nitrate solution used Moles of lead(II) ions 0.00050 mol Volume of potassium iodide solution used 7.0 mL Moles of iodide ions 0.00175 mol Theoretical yield of lead iodide (moles) 0.00050 mol Mass of dry filter paper PRO version 2.0 mL Are you a developer? Try out the HTML to PDF API 0.842 g Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Mass of filter paper plus dry lead(II) iodide 1.117 g Mass of lead(II) iodide prepared 0.275 g Molar mass of lead(II) iodide 360.22 g/mol Moles of lead(II) iodide prepared: “total yield” 0.000763 mol Percent total yield of lead(II) iodide 152% Mass of empty watch glass 18.634 g Mass of watch glass plus lead(II) iodide 18.844 g Mass of lead(II) iodide isolated 0.21 g Moles of lead(II) iodide isolated: “isolated yield” Percent isolated yield of lead(II) iodide Moles of lead(II) iodide lost during isolation Percent total yield lost during isolation process 0.000583 mol 76.4% 0.000180 mol 23.6% A. Data for the synthesis of manganese(II) chloride Mass of empty beaker 47.173 g Mass of beaker plus manganese 47.230 g Mass of manganese used 0.058 g Moles of manganese used 1.05 x 10 -3 Theoretical yield of manganese(II) chloride (moles) 1.05 x 10-3 Mass of empty beaker (same os above) 47.173 g Mass of beaker plus manganese(II) chloride 47.298 g Mass of manganese(II) chloride prepared Molar mass of manganese(II) chloride Moles of manganese(II) chloride prepared Percent yield of manganese(II) chloride 0.126 g 125.84 g/mol 1.00 x 10-3 95.2% Conclusion This experiment had a yield of 152% for the lead(II) iodide (75.4% of which was isolated) and of 95.2% for the manganese(II) chloride. If fact there is nothing in this experiment that PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 proves the products are rally what they are claimed to be, but, it is assumed the provided equations are the most likely to have happened and the reagents do not react with the atmosphere. For the preparation of lead(II) iodide, not only the total yield was recorded, but also the isolated yield. This value is very important because it is the working value. If the product was prepared for resale or for further reaction and that 23.6% was lost in the filtration, the procedure wouldn’t be very good and changes should be consider to obtain a higher yield. In this experimental process, the product wasn’t of further use, so the isolated yield is not that important. To improve the isolated yield, the filter paper could be changed for one with less stickiness or methods other than filtration could be used altogether. A substance could be found were the spectators ions have an higher Kps then in water and then, water could be evaporated to leave only the precipitate. Or, solutions of pure Pb2+ and I- could have been prepared by precipitating the other ions by reactions that leave those reagents as spectator ions. If a precipitation reaction was conducted using lead(II) nitrate and potassium sulfate, the product would be lead(II) sulfate, an insoluble compound. That reaction can be summarized by this equation: Pb(NO3)2(aq) + K2SO4 PbSO4(s) + 2 NO3SO4(aq). If the same proportions of lead ions and anion were to be used, the yield would be of 0.152 g. (PbSO4(s) has a molar mass of 303.26 g/mol) After the precipitation reaction, the concentration of each ion was: 0.11 mol/L I⁻ ( ); 0.14 mol/L NO3⁻ ( ); 0.18 mol/L K⁺ ( ); 0 mol/L Pb2+. The redox reaction can be written as the addition of an oxidation and a reduction. The electron lost by Mn(s) during the oxidation (shown as loose electrons on the right hand side of the first equation) are gained by the oxidizing agent H+ during the reduction. Mn0(s) + Mn2+(aq) + 2 e1-(aq) H20(g) + 2 Cl1-(aq) 2 H1+(aq) + 2 Cl1-(aq) + 2 e1-(aq) Mn0(s) + 2 HCl0(aq) MnCl20(aq) + H20(g) In this reaction, manganese is the limiting reagent. This means the real product obtained is a solution of hydrochloric acid and manganese(II) chloride in water. The acid and the water are then evaporated to isolate the halide. If not all of it is evaporated, the percent yield of the reaction can be shown as being more then 100% like in part A of this experiment where the product wasn’t truly dry, leading to an aberrant yield of 152%. Back to the manganese compound. If, on the other hand, the halide is overheated and start degrading, creating, as suggested MnO, the error produced will be negative. The molar mass of MnCl2 being greater than the one of MnO, the product will get lighter and Cl2 might be produced. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 To minimize those sources of error, it could be temptation to let water evaporate slowly, or to let the solid cool slowly on the open air. But MnCl2 tends to be hydrated. This is, to form bounds with water molecules as a solid without dissolving. The hydrated form probably does not have the pink color of the anhydrous form, but, most importantly, it has a greater molar mass. With the method used, it is more likely the product go decomposed then any other of the possible errors cited above. If a spill of HCl happened, possible steps to clean it up would be: -Neutralization with NaOH . -Dabbing with a cloth. References Simpson, Robert S.. Lighting control-technology and applications. Boston, Massachusetts: Focal Press, 2003. Encyclopaedia Britannica online “sodium hydroxide” on Nov. 7 2010. http://www.britannica.com/ Kotz, John C., et al. Chemistry and Chemical Reactivity. 6th edition. Belmont, California: Thomson Brooks/Cole. Chemistry 205 Experiment 5: Solubility Prelaboratory Questions 1. Procedure (N.B. note observations throughout) Put a small amount of each substance in clean vials. - Pour 1 mL of water to the substances, try to make them dissolve, add water if needed. Clean the stirrer between each use to avoid contamination. Test conductivity. Clean the conductivity tester between each use and test in distilled water. Add 1 drop of HCl to each vial. Neutralize and discard of the solutions. Repeat from the start with NaOH instead of HCl Chemistry 205 Experiment 5: Solubility PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Laboratory Report Observations and conclusions Magnesium Observations Conclusions Appearance Fine gray powder Substance type: Element With water Dissolution equation: Powder doesn’t dissolve at all. Suspends for about 2 seconds. Mg(s) + H2O → Mg(s) (no reaction) Conductivity None With acid Gas-forming, exothermic solution. Dissolves. Reaction: Mg(s) + 2H+(aq) +2Cl-(aq) → MgCl2(aq) + H2(g) (Redox) With base No reaction. Reaction: Mg(s) + Na+(aq) + OH-(aq) → Mg(s) + Na+(aq) + OH-(aq) (no reaction) Theoretical Solubility: None in water, reacts with acid. Calcium Oxide Observations Conclusions Appearance White, chalky, soft powder. Substance type: Ionic compound (Metal oxide) With water Dissolve partially, turbid white saturated solution. Dissolution equation: CaO(s) + H2O(l)→ Ca(OH)2(aq) (Acid/Base) Conductivity Good With acid Dissolve to a clear solution. Forms gas. Reaction: Ca(OH)2(aq) + 4 H+ (aq) + 4 Cl-(aq) → CaCl2(aq) + 2 H2O(l) + H2(g) + 2 Cl-(aq) (Acid/Base) With base No changes. Reaction: Ca(OH)2(aq) + Na+(aq) + OH-(aq) → Ca2+(aq) + 3 OH-(aq) + Na+(aq) (no reaction) Theoretical Solubility: Soluble in water, form a weak acid. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Sodium chloride Observations Conclusions Appearance White small cubic crystals Substance type: Ionic compound. With water Dissolution equation: NaCl(s) → Na+ (aq) +Cl-(aq) (no reaction) Dissolves. Conductivity Weak With acid Nothing changes. Reaction: Na+(aq) + H+(aq) + 2 Cl-(aq) → Na+(aq) + H+(aq) + 2 Cl-(aq) (no reaction) With base Nothing changes. Reaction: 2 Na+(aq) + Cl-(aq) + OH-(aq) → 2 Na+(aq) + Cl-(aq) + OH-(aq)(no reaction) Theoretical Solubility: Soluble in water. Tin Observations Conclusions Appearance Irregular, bronze colored, metallic granules. Substance type: Element (metal) With water Does not dissolve Dissolution equation: Sn(s) → Sn(s) (no reaction) Conductivity None With acid Granules turn silvery, liquid is cloudy. Reaction: Sn(s) + H+(aq) +Cl-(aq) → Sn(s) + H+(aq) +Cl-(aq) (low reactivity) (Redox) With base Granules turns silvery, phases of clear liquids. Reaction: Sn(s)+ Na+(aq) + OH-(aq) → Sn(s)+ Na+(aq) + OH-(aq) (low reactivity) (Redox) Theoretical Solubility: None in water. Ammonium chloride Observations PRO version Are you a developer? Try out the HTML to PDF API Conclusions Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Appearance White tiny grains. With water Clear solution. Conductivity Good Substance type: Ionic compound (cation and halogen) Dissolution equation: NH4Cl(s)→ NH4 +(aq) + Cl-(aq) (no reaction) With acid Less viscous, clear solution. Reaction: NH4 +(aq) + 2 Cl-(aq) + H+(aq) → NH4 +(aq) + 2 Cl-(aq) + H+(aq) (no reaction) With base Meniscus increases. Reaction: NH4 +(aq) + 2 Cl-(aq) + Na+(aq) + OH-(aq) → NH3 (aq) + H2O(l) + 2 Cl-(aq) + Na+(aq) (Acid/Base) Theoretical Solubility: Soluble in water. Sucrose Observations Conclusions Appearance White crystal-ish granules. Substance type: Covalent compound (carbon hydrate) Dissolution equation: C6H12O6(s)→ C6H12O6(aq) (no reaction) With water Clear solution. Conductivity None With acid Clear solution. Reaction: C6H12O6(aq) + H+(aq) +Cl-(aq) → C6H12O6(aq) + H+(aq) +Cl-(aq) (no reaction) With base Clear solution. Reaction: C6H12O6(aq) + Na+(aq) + OH-(aq) → C6H12O6(aq) + Na+(aq) + OH-(aq) (no reaction) Theoretical Solubility: Soluble in water. Sodium bicarbonate Observations Conclusions Appearance White powder Substance type: Ionic compound With water Dissolution equation: NaHCO3(s)→ Na+(aq) + HCO3-(aq) (no reaction) Clear solution Conductivity Good With acid PRO version Are you a developer? Try out the HTML to PDF API Clear solution Reaction: Na+(aq) + HCO3-(aq) + H+(aq) +Cl-(aq) → Na+(aq) + HCO3-(aq) + H+(aq) +Cl-(aq) (no reaction) Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 With base Clear solution. Reaction: 2 Na+(aq) + HCO3-(aq) + OH-(aq) → 2 Na+(aq) + CO32-(aq) + H2O(l) (Acid/Base) Theoretical Solubility: Soluble in water. Nickel (II) chloride Observations Conclusions Appearance Pale green powder. Substance type: Ionic compound With water Dissolution equation: NiCl2(s) → Ni2+(aq) + 2 Cl-(aq) (no reaction) Light applegreen solution. Conductivity Good With acid Nothing changes Reaction: Ni+(aq) + 2 Cl-(aq) + H+(aq) +Cl-(aq) → Ni+(aq) + H+(aq) + 3 Cl-(aq) (no reaction) With base Turquoise precipitate. Reaction: Ni+(aq) + 2 Cl-(aq) + Na+(aq) + OH-(aq) → NaCl(aq) + ClOH(aq) + NiOH(s) (Precipitation) Theoretical Solubility: Soluble in water. Potassium permanganate Observations Conclusions Appearance Dark purple Substance type: Ionic compound metallic needles. Dissolution equation: With water Purple solution. KMnO4(s) →K+(aq) + MnO4-(aq) (no reaction) Conductivity Good With acid Solution becomes dark orange. Reaction: 2 K+(aq) + 2 MnO4-(aq) + 16 H+(aq) + 16 Cl-(aq) → 2 Mn2+(aq) + 8 H2O(l) + 5 Cl2(aq) + 6 Cl-(aq) + 2 K+(aq) (Redox) With base Purple solution becomes darker. Reaction: K+(aq) + MnO4-(aq) + Na+(aq) + OH-(aq) → K+(aq) + MnO4-(aq) + Na+(aq) + OH-(aq) (no reaction) Theoretical Solubility: Soluble in water. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Additional Questions 1. This experiment proves the solubility trends exposed in this course’s manual: Chemistry and Chemical Reactivity (Kelps??). All the ionic compounds acted according to the rules learned. Covalent compounds, were soluble according to their polarity. 2. Solutes that tend to be insoluble in pure water but soluble is acid or base are metals.That is because there is a redox reaction between a transition metal and an acid that turn the metal into its ion. Substances that are only soluble in bases are rare. Chemistry 205 Experiment 6a: Analysis of an Unknown Oxide of Copper Prelaboratory Questions 1. -Place 0.15 to 0.20 g of copper oxide in a weighted beaker. Note the exact mass of the substance. -Add 2.5 mL of HCl. Swirl mixture and slowly heat until all the solid had dissolved. -Add 2.5 mL of water and 0.1 g of aluminum. Note observations. -Isolate the precipitated copper by decantation, rinse with acetone, dry on a low intensity hot plate. 2. (Molar masses from the Periodic Table of the Element provided at the Chem 205 mid term exam.) CuO: Molar mass is 63.55 + 15.999 = 79.55 g/mol Percent mass of copper: 63.55 / 79.55 * 100 = 79.88 % Cu2O Molar mass is ( 2 * 63.55 ) + 15.999 = 143.10 Percent mass of copper: ( 2 * 63.55 ) / 143.10 * 100 = 88.82 % 3. The color of CuO is: black The color of Cu2O is: reddish-brown 4.The color of Cu2+ (aq) is : blue The color of Cu+ (aq) is : red PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Chemistry 205 Experiment 6b: Gravimetric Determination of Carbonate or Bicarbonate Prelaboratory Questions 1.-Place about 0.2 g of the substance in a weighted beaker. Note the exact mass. Add HCl drop by drop until the reaction stops. Add 2-3 drops extra. -Boil the solution until truly dry. Let cool down. Note mass of remaining solid. 2.The boiling points are: NaCl: 1413 ˚C CO2: -78.5 ˚C HCl: 109 ˚C H2O: 100˚C This information shows that NaCl will be the last compound to boil in the present solution, therefor making evaporation an easy way to isolate the desired product. If the product we wanted to isolate had a boiling point close to the ones of other present substances, other means of separations would have had to be found. 3. 38 % HCl = 38 g per 100 g 100 g /1.2 g/mL = 83.3 mL 38 g / 83.3 mL = 0.465 g/mL 0.465 g/mL x 1000 mL/L = 456 g/L 465 g/L / 36.46 g/mol = 125 mol/L The molarity of concentrated HCl is 125 M. 4. a)Na2CO3(s) + 2 HCl(aq) → 2 NaCl(aq) + H2O(l) + CO2(g) Molar mass: 105.987 g/mol Moles in 0.2 g: 0.2 g / 105.987 g/mol = 1.88702 x 10-3 mol Concentration of the acid: 6 M = 0.006 mol/mL Volume of acid needed for reaction: (1.88702 x 10-3 mol / 0.006 mol/mL) x 2= 0.629 mL 0.63 mL of HCl are needed. b)NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g) Molar mass: 84.005 g/mol Moles in 0.2 g: 0.2 g / 84.005 g/mol = 2.3808 x 10 -3 mol Concentration of the acid: 6 M = 0.006 mol/mL Volume of acid needed for reaction: 2.3808 x 10-3 mol / 0.006 mol/mL = 0.3968 mL 0.40 mL of HCl are needed. 5. In baking powder, NaHCO3 is used conjointly with monocalcium phosphate to PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 create an acid-base reaction that yields Co2. The balanced equation of this reaction is: 2 NaHCO3(s) + Ca(PO4)2(s) → 2 Na+(aq) + 2 CO2(g) + 2 H2O(l) + Ca+(aq) + ½H2(g) + 2 PO43-(aq) In some recipes, baking soda is used alone because the batter is acidic enough to make rise without Ca(PO4)2. In that case, the equation is: NaHCO3(aq) + H+(aq) → Na+(aq) + CO2(g) + H2O(l) Chemistry 205 Experiment 6A: Analysis of an Unknown Oxide of Copper Laboratory Report Data and Observations 1. Upon addition of HCl, unknown #1: Turns dark green, with excess solute. The solution look lighter as the solute dissolves. Extra HCl is needed. There is condensation on the beaker. When water is added, the color is more diluted and look bluer. Some of the copper oxide never dissolves. 2. Upon addition of the aluminum to the solution: reacts immediately, forms a gas. tiny droplets of copper are formed. Heat is produced, solution is clear, with gray suspensions. Aluminum dissolves. Reaction slows down with time. The copper are balls are soft and spongelike. 3. Mass of beaker (g) 47.194 Mass of beaker plus copper oxide (g) 47.366 Mass of copper oxide (g) 0.172 Mass of beaker plus copper (g) 47.340 Mass of copper obtained (g) 0.146 Moles of copper obtained (mol) Mass of oxygen in the copper oxide (g) 0.026 Calculation and Analysis 4. Based on the prelab, the unknown substance would be CuO, copper(II) oxide because the powder form is black. PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 5. The oxide copper is 84.9% copper and 15.1% oxygen. It is impossible to determine which oxide it is based on this result because the choices are 79.88% copper or 88.82% and the result about the average for CuO or Cu2O. 6. The research done for the pre-laboratory does not support the result of the laboratory because the percent error is too great. (6.28% for CuO or 4.41% for Cu2O) it is evenm closer to the wrong result then the right one. Additional questions 1. Moles of copper oxide: 0.146/63.55 = 2.2974 x 10-3 mol Moles of HCl needed: CuO + 2 HCl -> Cu 2+ + H2O + 2 Cl- (aq) : 2 *2.2974 x 10-3 = 4.54 x 10-3 mL of HCl 6M needed: 4.54 x 10-3 /6 *1000 = 0.765 mL Percent of solution used that was in excess: (2.5-0.765)/2.5 *100 = 69.3 % Because more solution was added without noting volume, more then 69.3% of the HCl 8. The observed empirical formula is Cu1.4O1 (84.9/63.55) / (15.1/15.99) = 1.4146 Experiment 6B: Gravimetric Determination of Carbonate or Bicarbonate Laboratory Report Data and Observations 1. PRO version Mass of empty beaker (g) 49.965 Mass of beaker and unknown (g) 50.208 Mass of unknown (g) 0.243 Molar mass of sodium carbonate (g/mol) 105.987 Mole of unknown assuming it is sodium carbonate (mol) 2.29 x 10-3 Molar mass of sodium hydrogen carbonate (g/mol) 84.005 Mole of unknown assuming it is sodium hydrogen carbonate (mol) 2.89 x 10-3 Mass of beaker and sodium chloride (g) 50.131 Mass of sodium chloride (g) 0.160 Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Molar mass of sodium chloride (g/mol) 58.44 Moles of sodium chloride (mol) 2.738 x 10-3 1. The predicted yield of NaCl is 0.268 g for sodium carbonate. 1. The predicted yield of NaCl is 0.169 g for sodium hydrogen carbonate. 4. The most probable identity of the unknown is sodium hydrogen carbonate because the real yield of NaCl is closer (±0.009 g) to the one predicted for NaHCO3(s) then the one predicted for Na2CO3(s) (± 0.108 g). Additional Question 5. If sodium hydrogen carbonate was hydrated, its molar mass would have been greater (102 g/mol) and therefor, closer to the one of sodium carbonate, but the yield of NaCl per mole would still have differ a great deal because Na2CO3(s) + 2 HCl(aq) → 2 NaCl(aq) + H2O(l) + CO2(g) NaHCO3 H2O(s) + HCl(aq) → NaCl(aq) + 2 H2O(l) + CO2(g) 0 comments: Post a Comment PRO version Are you a developer? Try out the HTML to PDF API Downloaded by Rahil Kakkad (rahil.kakkad@gmail.com) New hot app: Facebook Albums To PDF pdfcrowd.com lOMoARcPSD|16644971 Home Subscribe to: Posts (Atom) ARE Y OU A DUMPER OR A DUMPEE? LABELS A wild wild summer. (5) PRO version Are you a developer? 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