Turnitin CHEM 111 separation of mixtures lab report PDF

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Destiny Cambero CHEM 111 – Farnum MTWR 9:40 AM 07/23/18

Experiment: Separation of Mixtures Conclusion: In conclusion, the Molarity of sodium carbonate in my first experiment was 112.07 M. In my second experiment the mass percent of my sodium chloride solution was 12.11%. In my final experiment the purity of my vanillin sample was 83.16%.

Experiment: Separation of Mixtures -Discussion The goal of this experiment was to figure out the concentration of mixtures through evaporation, to recrystallize a substance using vacuum filtration, and to determine melting point. To observe these changes, we performed three separate experiments simultaneously. These experiments allowed us to understand the different mechanisms used to separate compounds into their component parts using either physical or chemical methods. In our first experiment, we are using the method of gravimetric analysis to purify a substance, this consists of filtering the substance through a filter paper using gravity. The solid is collected in a funnel with the aid of the filter paper and the liquid filters through into a separate container. The solid allows us to compare it to other substances through stoichiometry. Stoichiometry is a method that uses quantitative relationships and ratios to determine the products and reactants in a given reaction. The reaction in this experiment is a double displacement reaction of the addition of aqueous calcium chloride to sodium carbonate, CaCl2(aq) + NaCO3(aq) -> CaCO3(s) + 2NaCl(aq), this will allow us to determine the molarity of a sodium carbonate solution. In the second experiment, we will be determining the mass percent of sodium chloride in our unknown solution. We will do this by simply heating the solution to remove the water content by evaporation, this can also be done by vacuum filtration but for this experiment we will use heat. In our final experiment, we will be determining the purity of a sample of vanillin by recrystallization. Vanillin is hydrophobic, meaning it will not readily dissolve in water at room temperature. Therefore, we will heat the sample to increase the solubility and separate it from impurities. A decrease in purity causes the melting point to have a larger melting range. Melting point is a physical property that can help determine a compound and its purity. For this experiment, we used instruments that allowed us to heat and filter our samples. We made sure to use instruments such as graduated cylinders, burets, and pipettes to ensure that our measurements were accurate and to minimize the formation of any error. For our first experiment, I observed that my sodium carbonate and calcium chloride solution became a clear liquid to a goopy white consistency. It looked like glue or pudding in terms of color and physical appearance. We needed to make sure that we used a filter paper that was the correct size for our funnel. There was a large and small size, the small size would be used in this experiment and the large one later. I almost had an error in terms of the filter paper because I had weighed the paper before tearing a piece off and once I returned to my bench I realized I had an incorrect measurement. I then tore the filter paper and reweighed it preventing a possible error. It is important to not pour the mixture too quickly into the funnel so that the sample doesn’t spill out causing error. Also, when wetting the filter paper and removing any residue in the funnel we want to make sure to use DI water so that we do not get any impurities from the tap water into our sample. I let my sample sit and filter while I performed my other experiments, the solution was thick so it took some time to filter. For the second experiment, we heated our sample using a Bunsen burner, to make sure that we didn’t overheat the sample while drying we made sure to place the evaporating dish over a beaker filled halfway with water. If we did not use the beaker with water we risk overheating our sample or having our sample pop out of the evaporating dish resulting in error. Once the evaporating dish is dry, we need to make sure that we let the dish cool completely, if we measure the dish when it’s too hot we risk getting an inaccurate mass reading and breaking the scale. For our final experiment, we were required to also heat our

vanillin sample but we only had one Bunsen burner per student, therefore we used a hot plate to perform this part of the experiment to gently heat our solution. After heating our solution till it dissolved we were to place it in an ice bath to chill. I observed that you needed to chill the sample for a sufficient time for ice crystals to form. Once they did we began to vacuum filter our solution without overfilling the funnel to prevent spilling. This is where we filter with the large filter paper instead of the small size that was used for the gravity filtration. An error I almost made was preparing the 20ml of cold DI water to wash the collected vanillin, although I had collected DI water I had added ice to the water to cool it down. This however would have been an error because the ice consisted of tap water not DI. A classmate stopped me before I used this solution and instead I collected a new beaker of DI water and let the beaker sit in the ice bucket while filtering. I had hypothesized that the gravimetric filtration would be the best method of removing impurities and the separation of compounds. This method was a good choice for the sample vanillin but there is a possibility it may not have been as affective with a different substance. Different mechanisms may be good or bad for different elements that have very different chemical and physical properties. It is good to select a method based on these properties. In this experiment, I believe I had little to no error. I almost encountered two different forms of error when I weighed my filter paper before removing a piece and by adding tap water ice to my DI water, however these errors were avoided. Based on the instruments and personal use I believe I had good precision and accuracy. For my first experiment, I found that the Molarity of my experiment was 112.07 M. This was found by taking the moles of Na2CO3 and dividing it by 0.0100L. For my second experiment, I discovered that my mass percent of sodium chloride in my solution was 12.11%. This was found by dividing the mass of my NaCl by 100ml of my solution and multiplying this by 100. For my final experiment, I found that the purity of my sample of vanillin was 83.16%. This was found by taking the mass of vanillin I had collected divided by the crude vanillin, all multiplied by 100. The major results in this experiment was my Molarity for experiment one, the mass percent in experiment two, and the purity in my third experiment. I didn’t have any visible errors throughout any of my experiments that could have affected the calculations. We did not calculate the standard deviation or the relative standard deviation for this experiment because we did not have enough data and it was not required. Conclusion In conclusion, the Molarity of sodium carbonate in my first experiment was 112.07 M. In my second experiment the mass percent of my sodium chloride solution was 12.11%. In my final experiment the purity of my vanillin sample was 83.16%. Errors Errors that occurred throughout my experiment was that I could not get all my vanillin out of my funnel. I scraped the sides of the funnel multiple times but there was still some vanillin in the creases that I could not get. Since I did not get all of the vanillin out of the funnel this could create some error in my calculations. A second error that occurred was that I collected 20ml of sodium carbonate solution for my second experiment but I was supposed to use 20ml of my unknown salt solution which was labeled #4. I did not use the sodium carbonate but I had measured out the 20ml to use in my experiment. Another error that I had was that I did not wash the sodium chloride and calcium carbonate solution with 15ml of DI water, so I may have collected all of my sample. Two errors that could have occurred could have been that I did not weigh my filter paper after tearing a corner off. This would have resulted in an incorrect mass

reading and incorrect data. A second error that could have occurred is that I did not use DI water or I added tap water ice cubes to my cold water needed to wash my vanillin. If I used tap water I would have added the impurities from the tap water contaminating my sample. Experiment: Separation of Mixtures –Post Lab Questions 1. In part A, what is the purpose of weighing the filter paper? How would your results change if you weighed the filter paper before you removed the corner? The purpose of weighing the filter paper is to get an accurate measurement of its mass. There is no reason to include the mass of the filter paper before the tear because it is not the current mass. We want the most updated mass so that we may subtract this later to get the mass of the solid. If we had the mass of the filter paper before the tear then this would lead to a higher mass of the filter paper than what there actually was leading to a lower mass of the solid even though the mass of the solid should be higher. 2. If you forgot to weigh the filter paper prior to adding the liquid, in any part of the experiment, how would your results change? The liquid would also add mass to the sample, if we were to weigh the paper after adding the water then this would lead to an inaccurate mass. If we were to weigh the paper after adding the water then we would be weighing the mass of the filter paper and the water, not just the filter paper itself. The liquid however should eventually dry, so if we were to weigh the sample during the next class session then the water should have evaporated. So as long as we weigh the filter paper before adding the water, any additional water shouldn’t affect the filter paper because the water should evaporate. 3. In part A, what is the basic assumption of this part that allows you to calculate the results? If a student accidentally used 25ml of the calcium chloride solution and used 20ml of the sodium carbonate solution, how would the students results be changed? Since we are given the volume and molarity of the samples we should be able to find the moles as well. However, if the student added 25ml of calcium chloride and 20ml of sodium carbonate then the ratios would be off. Had it been 20ml and 20ml then it wouldn’t have much of an affect, but the additional 5ml would affect the stoichiometry of the solutions giving different results. 4. In part A, what is a simple chemical test that will confirm the presence of a carbonate in your product? A chemical test that could confirm the presence of a carbonate could be adding a few drops of HNO3. If fizzing occurs then there is carbonate present if there isn’t any fizzing then no carbonate is present. 5. In part B, instead of using a large evaporating dish, a small evaporating dish was used. Assuming this change did not cause more sodium chloride to be lost during the experiment, how will your results change? Using a small evaporating dish would lead to less dish mass to be subtracted. Using a smaller dish could also cause the sample to take longer to dry. However, if no mass is lost, then there shouldn’t be much of a significant difference in the results. 6. In part B, a student used 15ml of the unknown sodium chloride solution. What will this change in the experiment and how can the student correct this error? By adding 15ml instead of 20ml we are missing 5ml of solution which will lead to a lower mass percent than there should be for the sample. To correct this error the student

can add the missing 5ml. If the student has time they can also perform the experiment again with just the 5ml and add the mass of that to the mass of the 15ml dried solution. 7. In part B, the student performing the experiment was feeling rushed and did not allow all of the water to evaporate. The student placed the evaporating dish and salt solution in the drawer to be measured the next class meeting. How will the results be changed? What is the disadvantage to this change in the protocol? There could be a possibility that the water hasn’t completely dried, this would lead to an inaccurate measurement because we would be measuring the mass of the salt and the water/hydrate. We want just the mass of the solid so we need to make sure that we completely dry the sample, the time spent in the drawer should be an additional drying period, not the drying period itself. 8. In part C, how would the results be changed if the solution was not allowed to cool in an ice bath prior to filtration? Vanillin readily dissolves when it is heated but not at room temperature. We heat the vanillin to not only dissolve it but to purify it. The cooling period allows the pure vanillin to condense again, if we filtered the hot vanillin it would filter through instead of staying on the top of the filter paper. This would affect the amount of vanillin we are able to collect and lead to an incorrect mass reading. !...