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Laboratory procedures and their explanation
The development of learning objectives
Discussion of basic laboratory techniques
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Purpose:
The purpose of this lab was to figure out the percentage yield of PbI2 that will be produced along with confirming our hypothesis as to what the limiting reagent would be.
Hypothesis:
2NaI Pb(NO3)2 PbI2 2NaNO3
Mass (g) 3.00 2.00 2.78
Molar Mass (g/mol) 149.89 331.20 461
Moles (mol) .0200 .00604 .00604
Moles of Pb(NO3)2 = 2.00/331.20 Moles of NaI = 3.00/149.89
= .00604 mol = .0200 mol ( xPb(NO3)2)/(.0200 mol NaI)= ( 1)/2 ( xNaI)/(.00604 mol Pb(NO3)2 )= ( 2)/1 2x = .0200
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For part 1 the theoretical yield was predicted to be 2.78g. When the experiment was finished and the precipitate had rested in an incubator for 24 hours, the actual yield turned out to be 2.75g. 98.9% of the theoretical yield was created. For part 2, using stoichiometry the limiting reagent was predicted to be Pb(NO3)2 while the excess reactant was believed to be NaI. After conducting the test, our hypothesis was confirmed; Pb(NO3)2 was indeed the limiting reagent while NaI was the excess reactant. There were little to no anomalies in this lab.
Experimental error is something that always occurs, no matter how hard one tries to prevent it. One situation where error might have occurred would be in the mixing of the water and Pb(NO3)2 and mixing of the water and NaI solutions. The solids were not fully dissolved into the water and when mixed, the yellow solution had all the precipitate at the bottom of the beaker while the clear liquid remained at the top. The mixed solution was still all yellow in color but not all of it was the same shade of yellow. This might have impacted the experiment by producing more PbI2 than it was supposed
The purpose for this experiment was to determine why it was not possible to obtain a high percent yield when Calcium Nitrate Ca(〖NO_3)〗_2 with a concentration of 0.101 M was mixed with Potassium Iodate KIO_3 with concentration of 0.100 M at varying volumes yielding Calcium Iodate precipitate and Potassium Nitrate. Filtration was used to filter the precipitates of the solutions. The percent yield for solution 1 was 87.7%, and the percent yield for solution 2 was 70.8%. It was not possible to obtain a high percent yield because Calcium Iodate is not completely soluble and some of the precipitates might have been rinsed back to the filtrates when ethanol was used to remove water molecules in the precipitate.
The experiment was not a success, there was percent yield of 1,423%. With a percent yield that is relatively high at 1,423% did not conclude a successful experiment, because impurities added to the mass of the actual product. There were many errors in this lab due to the product being transferred on numerous occasions as well, as spillage and splattering of the solution. Overall, learning how to take one product and chemically create something else as well as how working with others effectively turned out to be a
The question that was proposed for investigation was: Can the theoretical, actual, and percent yields be determined accurately (Lab Guide pg. 83)?
There were no significant error factors that may have affected the arrangement of the lab experiment. Everything went smoothly with relative ease.
Living organisms undergo chemical reactions with the help of unique proteins known as enzymes. Enzymes significantly assist in these processes by accelerating the rate of reaction in order to maintain life in the organism. Without enzymes, an organism would not be able to survive as long, because its chemical reactions would be too slow to prolong life. The properties and functions of enzymes during chemical reactions can help analyze the activity of the specific enzyme catalase, which can be found in bovine liver and yeast. Our hypothesis regarding enzyme activity is that the aspects of biology and environmental factors contribute to the different enzyme activities between bovine liver and yeast.
Possible errors include leaving in the test strips for too long, draining too much water into the aquatic chamber (overfilling/watering), and inverting the tubes for a shorter amount of time than required. Although there are many possible human errors that could be committed in this lab, it is important to note that the tools used for water testing could be expired and could therefore not work as well at detecting the proper levels for dissolved oxygen, pH, and nitrate.
According to the graph on amylase activity at various enzyme concentration (graph 1), the increase of enzyme dilution results in a slower decrease of amylose percentage. Looking at the graph, the amylose percentage decreases at a fast rate with the undiluted enzyme. However, the enzyme dilution with a concentration of 1:3 decreased at a slow rate over time. Additionally, the higher the enzyme dilution, the higher the amylose percentage. For example, in the graph it can be seen that the enzyme dilution with a 1:9 concentration increased over time. However, there is a drastic increase after four minutes, but this is most likely a result of the error that was encountered during the experiment. The undiluted enzyme and the enzyme dilution had a low amylose percentage because there was high enzyme activity. Also, there was an increase in amylose percentage with the enzyme dilution with a 1: 9 concentrations because there was low enzyme activity.
The purpose of this assessment was to research, design and conduct an experimental investigation on the effect of substrate concentration (manipulated by increasing concentration of pH buffer) of catalysed reactions by measuring the volume of oxygen produced as the reaction proceeded.
A precipitation reaction can occur when two ionic compounds react and produce an insoluble solid. A precipitate is the result of this reaction. This experiment demonstrates how different compounds, react with each other; specifically relating to the solubility of the compounds involved. The independent variable, will be the changing of the various chemical solutions that were mixed in order to produce different results. Conversely the dependent variable will be the result of the independent variable, these include the precipitates formed, and the changes that can be observed after the experiment has been conducted. The controlled variable will be the measurement of ten droplets per test tube.
Using your finger, gently tap the tubes to mix the Luria broth with the cell suspension. The test tubes will need to rest for approximately five to fifteen minutes in a room temperature environment.
The difference between endothermic and exothermic reactions is that endothermic absorbs heat and exothermic releases heat. For example, an endothermic reaction was performed in reaction four. Reaction four is where we recorded the temperature of the acetic acid before the reaction took place. We left the thermometer in the solution and poured sodium bicarbonate into the acetic acid. The result was the product dropped 6°C, this was an endothermic reaction because it lost heat, or had the cooling effect. The example for an exothermic reaction was reaction two. We placed a piece of aluminum in CuCl2 and waited for the reaction. The aluminum produced a gas and the product became hot to the touch. This is an example of an exothermic reaction because heat was exerted.
Limiting factors are components or conditions of an environment that prevent a population from continually growing. Nutrients are one type of limiting factor that can affect the growth of a population. Bacteria, for example, are unable to synthesize fundamental chemical elements necessary for growth, therefore, they rely on their environment to provide these important factors. While the bacteria are growing, they are using up the supply of available elements, and as growth continues, the element that is present in the lowest concentration related to the demand will eventually run out causing the bacteria to stop growing. Environmental factors can also limit the growth of a population. Bacteria are sensitive to the pH of their environment and if the pH is not within the optimal range for growth, bacteria may stop growing.
The heat of solution is the enthalpy change associated with the process of a solute dissolving in a solvent. With an ionic compound dissolving in water, the overall energy change is the result of two processes (the energy required to to break the ionic bonds between the ions in the lattice structure, and the energy released when the free ions form dipole attractive forces with the water molecules). Heats of solution are generally measured in an insulated container, called a calorimeter. The process of the dissolving solute either adds or subtracts heat from the solution. The amount of enthalpy change can be determined by using the equation, q=m•C•∆T, with the specific heat of the solution generally being the same as that of water, 4.18 J/g•C°.
Next, for Part B, “Equilibrium Measurements,” Fe3+ is reacted with thiocyanic acid and nitric acid according to the data in Table 2 across five trials. The initial concentrations of iron(III) ion and thiocyanic acid are noted in Table
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.