In the first part, five 100 mL flasks of 5 mL ligand solution, 5 mL 2 M sodium acetate, 4 mL 3 M NH2OH, and 1-5 mL Fe2+ solution are diluted with water. The absorption spectrum for varying concentrations of Fe2+ are measured using a spectrophotometer and the data is graphed in Excel. The slope of the line is ε in the Beer-Lambart equation A = εcl. In the second part of the experiment, eleven flasks containing diluted stock solutions of Fe2+ and ligand are mixed with 5 mL 2 M sodium acetate and 4 mL 3 M NH2OH and diluted with water. The absorption spectrum is measured using a spectrophotometer and the data is graphed in Excel.
c. Prepare the solution by dissolving 38.90 grams of ZnI2 with 500 mL of water. d. 0.0125/0.25 = 0.05 L = 50 mL. This produces 0.0125 moles of ZnI2 5. Exercise 5: a. (0.125)(0.1) = 0.0125 moles of solute b. Pour 50 mL of the stock solution to get the number of moles needed.
The real density of aluminum is 2.70 grams, the density we found was 2.69 grams. This made the present error -0.37%. A couple sources of error we could have had are reading the measurements on the graduated cylinder and scale and also we could have inaccurately recorded the data. In order to get more accurate data one could use a more specific scale, tested a few more times, or been more specific about the pieces of aluminum they used. The experiment did meet the overall goal, which was getting close to, if not hitting, the density of 2.70 grams and we came close with less than -0.5% percent
The half reactions for this system are: Oxidation of 〖Fe〗^(2+): 〖Fe〗^(2+)→ 〖Fe〗^(3+)+1e^- Reduction of 〖MnO〗_4^-: 〖MnO〗_4^-+8H_3 O^++5e^-→ 〖Mn〗^(2+)+12H_2 O Which produces the following overall equation: 〖MnO〗_4^-+8H_3 O^++5〖Fe〗^(2+)→5〖Fe〗^(3+)+〖Mn〗^(2+)+12H_2 O Equilibrium is initially obtained at a very slow rate, therefore the titration is carried out in the presence of excess sulphuric acid (H_2 〖SO〗_4) at a high temperature; in order to drastically increase the rate at which equilibrium is attained. Potassium permanganate acts as its own satisfactory indicator since the reagent 〖MnO〗_4^- anion appears to be an intense purple colour while the product 〖Mn〗^(2+) cation has a colourless appearance. However, the end point must be read quickly as the permanganate end point gradually fades due to the 〖MnO〗_4^- reacting with the 〖Mn〗^(2+) that was formed during the titration. When performing the titration, one must be cautious as side reactions can occur and these side reactions must be prevented using appropriate chemical measures. If an insufficient amount of acid was
Lab 4 – Energy Sources and Alternative Energy Experiment 1: The Effects of Coal Mining |Table 1: pH of Water Samples | |Water Sample |Initial pH |Final pH (24-48 hours) | |Pyrite |6 |6 | |Activated Carbon |6 |7 | |Water |6 |6 | POST LAB QUESTIONS Develop hypotheses predicting the effect of pyrite and coal on the acidity of water? Pyrite hypothesis = I would guess ph would be lower. Coal hypothesis = I would guess ph would be higher. Based on the results of your experiment, would you reject or accept each hypothesis that you produced in question 1? Explain how you determined this.
Discussion and Conclusion In this experiment, the bromination of an alkene will be observed and a mechanism to account for the occurrence distribution of the products will be determined. In the first part of the experiment the 0.9 grams of E-stilbene will be put in a flask with 10ml of dichloromethane and then stirred to affect dissolution of the E-stilbene, since dichloromethane is a nonpolar solvent which can dissolve the nonpolar alkene. After the E-stilbene has been dissolved, 5ml of bromine in dichloromethane will be added, which will be stirred for thirty minutes until the solution is white, to ensure that the reaction has gone to completion. Bromine in dichloromethane is used because dichloromethane works as a good solvent for bromination reactions, due to the fact that it doesn’t react with bromine or most other organic molecules. The reddish color of bromine is discharged upon addition to an alkene as the bromine reacts, making this reaction a useful qualitative test for unsaturation when the reaction has gone to completion.
Our scale only measures to grams accurately, and could have not accurately represented the .68g of CaCO3, or we could have lost the solid precipitate in the process of the experiment. These errors could be reduced with a more accurate scale, as well as more experienced hands performing the procedure, or skilled hands, ie: we are novices at this lab, and training could produce more accurate
The smaller amount will ‘limit” how much the reactant can produce. A percent yield in a chemical equation is used because chemical reactions do not predict amount of a substance. The percent yield is usually determined by the mass that is in the chemical reaction. A percentage will be produced from using the formula; This percentage is the calculation of your success of producing a product compared to the total amount of a product that can be produced. The familiar volcano experiment that we all know, mixing baking soda and vinegar, is used to create a bubbly reaction.
The only variable that is changing is the temperature meaning that the temperature and the heat of reaction have a positive correlation. If the temperature increases then the value for the enthalpy change will increase, and vice versa. All measurements, observations and calculations were carefully checked and are therefore not a source of error. One source of error could be that the calorimeter (Styrofoam cup) was uncapped and not a perfect insulator for keeping the heat from escaping. As it was uncapped some of the heat would have been lost to the air and as one of our assumptions was that the heat released by the reactions was used only to heat the water the value calculated will be off.
Add a quarter spatula of copper (II) oxide and warm the solution gently to the 4th test tube and record observations. 7. To the 5th test tube, add 3cm3 of ethanol a couple of drops of conc, sulphuric acid and warm gently. Pour the resulting mixture into 30cm3 of sodium carbonate solution to remove excess acid and smell and record observations. Experiment 2 Time | Observations | 5 minutes | Bubbled like sugar | Once salt water was added | Turned soapy white and thick | Equation: METHOD 1) Put 2 cm3 of castor oil into a 250 cm3 beaker and add 10 cm3 of 5mol.dm-3 sodium hydroxide from a measuring cylinder.