OBJECTIVE:
To determine the equilibrium constant for the following reaction:
Fe3+(aq) + SCN-(aq) -----> Fe(SCN)2+(aq)
BACKGROUND:
In this experiment, the equilibrium constant, K, for the above reaction is given by the expression:
K = [FeSCN 2+]
[Fe 3+][SCN 1-]
where the concentrations of the substances are those at equilibrium. The equilibrium concentrations of these substances will be determined and used to determine K.
Since the reactants are essentially colorless, whereas the complex ion product is deeply colored, a spectrophotometer will be used to determine the maximum absorbance due to the FeSCN2+at its four different concentrations. Beer's Law states that the absorbance of a colored solution is directly proportional to the concentration of the absorbing species. In this experiment, the FeSCN2+ is the absorbing species. The formula for Beer's Law is A = kc where A is the absorbance of the solution, k is the Beer's Law constant and c represents the concentration of the absorbing species. To make easier to calculate the equilibrium concentration of FeSCN2+, the concentration vs. absorbance is plotted on the graph. Then the formula of Beer's Law is C = kA. To make the constant k more significant number, the concentration values will be used in mmol/L.
The experiment will be done in two parts. In the first part the value of the Beer's Law constant, k, will be determined and in the second part, the Beer's Law constant and the absorbance will be used to determine the equilibrium concentration of FeSCN2+. After the equilibrium concentration of Fe(SCN)2+ will be measured by way of the absorbance, the concen...
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...sed, the equilibrium absorbance increased. The value of K is much larger than 1, so the equilibrium is said to lie to the right. The reaction is exothermic, heat is a product; the concentrations of the products are much greater than the concentrations of the reactants. The equilibrium constant is determined to be 188. This value was the same in the mixture 2 and 3. In the first mixture the K is much larger - 200, while the mixture 4 and 5 are 185 and 182. Because a balance, equilibrium constant exists when the ratio of product concentrations to reactant concentrations does not change through further reaction, there is an error in the experiment. The K values are not precise. Only two of them have the same number. The error could be done by a temperature change that is the only form of stress to an equilibrium system that changes the value of the equilibrium constant.
The essential points of the green-frosting are the concentration and absorbance value in each diluted which the process of serial dilution. The standard curve of Blue#1 and yellow #5 provide the equation of the trend-line in order to calculate the concentration in the diluted solution of the green frosting. The mole of dye in 100mL green stock solution, mole of dye in 5 gram and 1 gram of frosting, the Beer –Lambert Law, and the compare to amount desired by the company can be determined. The Beer-Lambert Law is the relationship between color and the concentration and equation A=Ebc. The “A” is absorbance, the “C” is a concentration in molarity, the “E” is a molar absorptivity and “b” is the path-length. The goal of the lab is to use the absorbance and the Beer-Lambert law to determine the amounts of blue#1 and yellow #5 in the green frosting.
where 'n' number of ligands attached to a metal ion which can be easily determined from the position of the maximum or minimum in the graph. If the metal ion and the ligand are colorless, but the complex species is colored, then there will be maximum at the composition of the complex in the plots of absorbance versus composition.
this solution we had to weigh out 5g of KHP, which is the amount needed to
...eases, including temperature. It is determined from the data that the reaction is more likely to have a step wise mechanism than a concerted due to the small – ΔS and a relatively large value of ΔH from the tables. Due to some errors, it is best to perform another experiment for future protocols. In addition with the variance the 35°C where at one point the absorbance levels off and then increases. In comparison to the rate constant against temperatures, at 25°C it is higher than 35 and 45. More test is required to ensure proper determination of the rate constant at those temperatures.
For these calculations assume the temperature remains constant at 25 °C. There are four steps here. First the initial concentration of CoCl2(iPrOH)2 needs to be determined. Second, the equilibrium concentration of CoCl2(iPrOH)2 must be found. Third is the calculation of the equilibrium concentration of CoCl2(MeOH)4, then fourth, the ratio [CoCl2(MeOH)4] / [CoCl2(iPrOH)2] at equilibrium. Show all work. Remember to state the equations you are using defining all variables and constants. Then substitute in the values and show the results. Be certain all sig figs and units are correct. You are expected to follow this format in all subsequent lab work without being prompted.
Our most basic knowledge of chemical equilibria comes from a French man named Henry-Louis Le Chatelier. Through his studies of equlibria and the effects of changes provoked on these equilibria, he was able to come up with a principle that is studied widely today. Le Chatelier’s Principle, which was named after him, states that a change in one of the variables in a system at equilibrium will cause a shift in the position of the equilibrium that counteracts this system. Le Chatelier’s Principle is aimed at three changes that can cause a disruption in a system at equilibrium. These three changes include a change in the temperature of a reaction, a change in the concentration of one of the variable of a reaction, and a change in the pressure on a system. [1]
2. Put the test tube inside a beaker for support. Place the beaker on a balance pan. Set the readings on the balance to zero. Then measure 14.0g of KNO3 into the test tube.
using the control (“Blank”) as you did in the previous experiments. The contents of test tube 2 and 3 were mixed in a clean (clear of fingerprints) and the absorbance changes at 15 second intervals for 60 seconds were measured. The results were recorded in Table 9.
The way we would expect to observe this context in the experiment would be by seeing the reaction of adding chemicals together and separating the chemicals to see if chemicals were destroyed, created or neither. The type of chemical reactions performed were that the same amount of mass in the reactants are the same amount of mass in the products. The most important component of a reaction of this type is to do the experiment process correctly to achieve the results meant. Using the properties of the reactants and products involved, predict the outcome of the reaction and describe the methods used to successfully perform the experiment. Based on our data the law of mass conservation was observed through the experiments containing ZnCl2(aq) + Na2S(aq) and Pb(NO3)2(aq) + 2 KI(aq). We gained mass after mixing the chemicals and separating the chemicals for both experiments. In the first experiment the difference in the amount mass from the initial mass was 0.46 g and in the second experiment there was a difference in the amount mass from the initial mass which was 0.75 g.
...eadings. The absorbance readings for test tube 5, were always further away from the expected values than test tube 1. This is because the NaOH was not added to each tube at a time, but in sequential order with the test tube numbers. This allowed the reaction in test tube 5 to proceed longer than in test tube 1, allowing more product to be produced, giving a higher absorbance reading than expected. In fact, this trend was shown in all the test tubes. In increasing order of test tube numbers, every absorbance was more off than expected.
Varying the n value carries out the experiment. Absorbencies of each of the ZLn complexes are obtained. The sum of the concentrations of the metal, Z, and the ligand, L, are kept equal. With the ratio of the ligand to the metal in the solution with the maximum absorbance for the ZLn complex, the value of n can be determined as well as the composition of ZLn.
The purpose of the experiment is to identify and understand reactions under kinetic and thermodynamic control. A reaction under kinetic and thermodynamic control can form two different types of products. A reaction under kinetic control is known to be irreversible and the product is formed quickly. A reaction under thermodynamic control is known to require rigorous conditions. It is also reversible. The final product is more stable than the product made by kinetic control. The chart below shows the two types of reaction coordinates:
Usually, potassium ion is not included due to low concentration and stable amount. Therefore, the calculation is adjusted as following:
This experiment consists of titrating the ferrous ion with permanganate ion to study the oxidation-reduction reaction. The ions react in acidic solution to give ferric ion and a reduced ionic form of manganese. All the reactants and products except permanganate ion are weakly colored, whereas permanganate is a very intensely colored ion. Then a solution of permanganate is removed as long as there is a ferrous ion present to react with it. But as soon as the entire ferrous ion has been oxidized, the next small portion of added permanganate colors the solution. The first appearance of a permanent pink color indicates the endpoint of the experiment. From the titration it will be able to calculate the percentage of iron in the sample from the data.
g. of KI in 10 mL of water. Add the KI solution dropwise to the test