Spectrophotometric Determination of Equilibrium Constant for a Reaction

From this graph and chart we can see that the higher the concentration the higher the absorbance, all the different concentrations were tested at the same wavelength (625nm). Also we can determine our unknown substances concentration by using the absorbance we got for it. The red dot on the graph followed by the line towards the horizontal axis indicates that the concentration of fast green was 34% or 5.1x10-3.

Time) because it had a correlation closest to 1. All three orders were graphed and a linear regression was used to see which graphed order was closest to 1. The order was determined by comparing the concentration and time to the mathematical predictions made using the integrated rate laws. Analyzing each graph and finding each correlation helped determine which graph was closest to 1. The more concentrated a solution is, the higher the absorbance of that solution. This is due to Beer’s Law. The law measures the absorbance of a solution by determining how much light passes through a solution. As the concentration of a solution increases, fewer wavelengths of light are able to pass through the concentrated solution. The absorbance at 60 seconds was 0.573 (Figure 1: Table1). To calculate the concentration (molarity), the Beer’s Law equation was used, Abs = slope(m)+b. Plugging in what is known into the Beer’s Law equation resulted in 0.573 = 3.172e+004 + 0, where the concentration is determined by M = 0.573-0/ 3.172e+004. So, the concentration at 60 seconds using the equation (M = 0.573-0 / 3.172e+004) was 1.824e-5 M. The 1st order graph resulted in k=0.006152 (Figure 1: Graph 1). Other groups also resulted in their decolorization of CV to be the 1st rate

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.

5. The degree of precision was to 3 significant figures obtained with the spectrophotometer. The major source of error in our experiment was not calibrating the spectrophotometer with distilled water.

The goal of this experiment is to prepare a photosensitive solution and explore its properties. While analyzing the solution, one will learn how to successfully handle these sensitive chemicals and then establish its properties via spectrophotometry.

A = Absorbance difference  = Molar extinction coefficient C = Concentration L = Path length

Next, we took initial absorbance readings in the Spec20 at an absorbance rate of 600 nm as well as an initial color reading. Then placed one sample under red, blue, green, or white light illuminators, and one sample in the dark. The cuvette placed under the white light acted as our positive control, and the cuvette placed in the dark acted as our negative control. We took absorbance readings of each cuvette every 5 minutes until we had four readings. After the fourth and final absorbance reading, we also took a final color reading.

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

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.

The absorbance with SDS shows a rapid increase, before the graph begins to increase more slowly and uniformly. The absorbance levels off at 0.9nm. The absorbance with no SDS remains at a constant level of 0.01nm for the entire experiment. The absorbance of the control solution is also constant throughout the experiment. This shows the absorbance of the compounds in the solution without the ovalbumin, by taking this figure away from the other recordings, it is possible to discover the absorbance for ovalbumin alone.

The results in Graphs and Tables 7 and 8 show that as the wavelength increases the percent transmittance as the absorption decreases. Graph 8 looks cleaner compared to Graph 7 which could be a human error when measuring and diluting the solutions or a potential error with the Spec 20 not reading it

intensity of light entering the cell (I0) and leaving the cell (I) are related by Beer’s Law. The

Light, Color, and Solutions Lab In this experiment, the relationships between wavelength, absorbance, concentration, and cell path are explored through separate, smaller experiments. These relationships can be combined to derive a single equation known as Beer’s Law. This equation is then used to identify an unknown solution’s formula weight.

Part 3 of the experiment utilized Spectrophotometry to determine the iron content in the iron (III) oxalate complex. The results were combined with findings from Part 1 and

Chemical equilibrium is the study of change within a chemical reaction and how far it will go to reach a dynamic equilibrium (Burdge). Dynamic equilibrium is defined as the constant movement of species in a chemical reaction, gone to incompletion while the rates of production and consumption are equal (Kf = Kr ) (Burdge). It differs from static equilibrium in that species are constantly being consumed and produced, it is dynamic movement (Fox). The concentration of such species do not change, it remains constant (Fox). The rate at which species are being consumed and produced is known as the equilibrium constant (K) (Burdge). Due to the fact that the concentration