Equilibrium Lab Report

With these absorbance numbers a concentration curve was constructed and the unknown solution was determined by finding the point of absorbance on the curve.

10 microliters of the sample is then added and the assay absorption is measured at 340nm. If absorbance was above 1.5, samples were diluted.

Aim: The aim of the lab “Chemical Equilibrium” is to observe the effects of changes in concentrations of products and reactants on the position of the equilibrium of given chemical reactions.

Scientists use an instrument called a spectrometer to quantitatively determine the amount of light absorbed by a solution. The primary inner parts of a typical spectrometer are described below. The spectrometer has a light source that emits white light containing a vast mixture of different wavelengths of electromagnetic radiation. The wavelength of interest is then selected using a monochromator (“mono” meaning one and “chromate” meaning color) and an additional exit slit. The separation of white light into different colors (wavelengths) is known as diffraction. The selected light then reaches the sample and depending on how the light interacts with the chemical compound of interest, some of the light is absorbed and some passes straight through. By comparing the amount of light entering the sample (P0) with the amount of light reaching the detector (P), the spectrometer is able to tell how much light is absorbed by the sample.

b. Describe the spectral curve of each target type with respect to its absorption and reflectance characteristics. (3)

This shows Le Chatelier’s principle as the system was able to neutralize the disturbance from its equilibrium.In this case, the change was the addition of molecules to the reactants. This caused an increase in the number effective collisions between the reactant’s molecules. Also, this raised the rate of the forward reaction. The system then has an increased amount of reactants and therefore has to travel in the forward direction to make extra products. This occurred in order to return the system to equilibrium by removing some of the excess reactants. By shifting in the forward direction, more products are being produced by the excess reactants. This ensures that the forward and reverse reaction rates are equal, which brings the system back to a state of

For the concentration experiment three different concentrations were made of the KMnO4. Three test tubes were filled with 4 ml of water. The first test tube had 1 ml of the 500 KmnO4 added to it. Then the second test tube had 1 ml from test tube one and 4 mL of water. For test tube 3, 1ml was taken from test tube two. Each concentration was placed into a dialysis tubing using the strings to tie off one end and the clamp to close off the other end. Before the dialysis tubing was placed in the beaker, 1ml of a sample was placed in a cuvette to blank the spectrophometer. Each stir plate was set on a low speed and the dialysis was hung in the water by a string. Every 5 minutes that passed a sample of 1 ml was taken and put into a cuvette. The cuvettes were placed in the spectrophometer to measure the absorbance of each solution. The measuremnts were then recorded in lab notebook. Once the measurements were documented, the average of absorbance and concentration was recorded.

1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Concentration (mM) y = 0.1897x R2 = 0.99

3. The spectrophotometer was set at 420nm. Distilled water was also used as the ‘blank’.

For this experiment we are looking to determine the equilibrium constant KC for this reaction, KC = [FeSCN2+]/([Fe3+]•[SCN-]. Using a spectrophotometer, we are going to determine the absorbance of FeSCN2+ with different concentration measurements.

In this experiment, two reactions were run to determine the molar absorptivity and the equilibrium constant of FeSCN2+. The main principles used in this lab are equilibrium, LeChatlier’s Principle, Beer’s Law and Spectrocopy. The first reaction was run to completion using LeChatier’s Principle and the second reaction was run to equilibrium. A spectrophotometer was used to measure absorbances. Using a graph of absorbance versus concentration of FeSCN2+ was used to determine that the molar absorptivity constant was 3670. Beer’s Law was used to determine that the average equilibrium constant was 33.1793.

The absorbance is measured using a Plate reader and a Standard curve is generated. Also, the different types of pipetting techniques are assessed in this Assay.

This experiment initially involved the synthesis of an iron (III) oxalate complex with the general

8) Steps 1 - 8 were repeated using the wavelengths of 360 nm to 900

We have timed each of the three experiments for 5 minutes to make sure that our results are correct. Thanks to the program, we got the transmittance and the absorbance, together with the graph portraying our results.