Determination of Sodium Salicylate in Face Wash Solution Lab Report

Colorimetry Experiment lab report Determination of Sodium Salicylate in Face wash solution Abstract: The main purpose of this experiment is to determine the amount of sodium salicylate that is found in face wash solutions and to be able to successfully use a colorimeter. In order to conduct the experiment, a standard solution will need to be used which is made up of distilled water and sodium salicylate from different concentrations. Preparing to calibrate equipment to ensure accurate results. After that using the face wash solutions to be able to determine the amount of concentration in face wash solutions by using calculations to determine the value of the amount of sodium salicylate in solution A. The results received from the experiment were very similar to the actual results which shows that the equipment used was calibrated carefully. The result received was 34.7mM and the actual value of concentration for solution A was 35mM. The observations that were present from this experiment was the different shades of purple in each cuvette, showing the different concentrations of standard solution present in the cuvettes. Introduction: The relevant equation used in this experiment: A = εlc • A = Absorption (no units) • ε = molar absorption coefficient • c = concentration (M) • l = path length (cm) when using the equation y=mx+c: • y=A • m=ε • x=c • c=l Research: What does a Colorimeter do? Colorimeters measure the “absorbance level of light waves” present (Colorimeter - an overview |ScienceDirect Topics). In an experiment, to determine the amount of light passing in a solution, a Colorimeter Is used, this is because it contains photocells. (Colorimeter - an overview |ScienceDirect Topics, 2020) How to calibrate a colorimeter? In order to calibrate a colorimeter, press the clear button on the colorimeter to make sure it resets to “0.00” and place the blank sample cuvette, which is filled with distilled water to ensure the reading reads 0.00 which shows that the colorimeter has been calibrated properly before starting the experiment (Colorimeter User Manual – Vernier, 2020). How to create a calibration curve in excel? In order to create a calibration curve in excel, create a table with x and y values. after writing x and y values, press the scatter graph option and a graph would be produced. In order to retrieve a gradient for the graph, press the trend-line graph to get a line of best fit and to click the “Display Equation on chart” button in order to receive the gradient of the line (How to Do a Linear Calibration Curve in Excel, 2020). Pre-lab questions: Q1. For which one of the following do you need to wear gloves? A. B. C. D. Sodium salicylate Iron (III) nitrate nonahydrate Nitric acid Distilled water Q2. Which substance may intensify fire? A. Sodium salicylate B. Iron (III) nitrate nonahydrate C. Nitric acid D. Distilled water Q3. What property does salicin demonstrate? A. Antibiotic B. Antacid C. Anti-bacterial D. Anti-inflammatory Q4. What is colorimetry used to determine? A. The colour of a sample B. The concentration of any solution C. The concentration of a solution which has colour D. The structure of a sample. Equipment: • 12 x test tubes • micropipette & tips • 100 cm3 volumetric flask • • • • weighing boat spatula analytical balance 3 x 10 cm3 pipette • • • • • • • • • • • • pipette filler vortex colorimeter 2 x 50 cm3 beakers 10 x cuvettes cuvette stand glass pen sodium salicylate solution iron (III) nitrate nonahydrate (ferric nitrate) 0.1 M nitric acid commercial facewash distilled water. Aim: The aims for this experiment are: • To be able to use a colorimeter correctly • To be able to create a calibration curve • To be able to determine the concentration of sodium salicylate found in face wash solutions. Objective: The way to achieve the aim for this experiment is to ensure that students are aware of how to calibrate equipment such as a colourimeter by using the reference sample and to look up any other key research prior to completing the experiment. This will allow the experiment to have accurate results. To achieve the aim for creating a calibration curve is to be able to research key information on how to create one on excel. To determine the concentration of sodium salicylate, the final and important aim of this experiment, we need to be able to successfully complete the first two aims of the experiment in order for the final aim to be achieved. Completing this experiment and using beer- lambert law would allow the final aim to be met. Procedure Method: Preparation of standard sodium salicylate and ferric nitrate 1. Place 6 test tubes into a test tube rack and label them 1-6. 2. Using a 10cm3 graduated pipette, Add the required amount of sodium Salicylate Into each test tube 3. Using a clean 10cm3 graduated pipette, add the required amount of distilled water into the required test tubes. 4. Accurately weigh 0.400 g of iron (III) nitrate nonahydrate (ferric nitrate) and transfer into a 100 cm3 volumetric flask. Dissolve in 0.1 mol dm-3 nitric acid and make up to the mark with the nitric acid. Preparation of calibration samples for analysis by colorimetry 1. Into six separate test tubes, labelled 1-6, transfer 0.1 cm 3 of your standard sodium salicylate solutions using a pipette. 2. Using a 10 cm3 graduated pipette, add 10 cm3 of acidified 10 mM ferric nitrate into each test tube. 3. Mix the solutions briefly using a vortex mixer. Preparation of face wash solutions for analysis by colorimetry Using the same method for “Preparation of calibration samples for analysis by colorimetry” as shown above. 1. transfer 0.1 cm3 of face wash solution into a test tube 2. Add to this 10 cm3 of acidified 10 mM ferric nitrate 3. Mix the solutions briefly using a vortex mixer. Analysis of samples by colorimetry 1. Transfer the weakest calibration standard solution into a plastic cuvette so that the cuvette is approximately ¾ full. 2. Measure the absorbance of the solution at 535nm using the colorimeter and record the value in a suitable table. 3. Repeat this process for the other calibration standards, going from weakest to strongest. Table of Results: Volumes required to produce the range of standard solutions: Test Concentration of Standard Volume of Distilled Water 3 (cm3) Salicylate (cm ) tube (mM) 1 100 4 4 2 80 3.2 4.8 3 60 2.4 5.6 4 40 1.6 6.4 5 20 0.8 7.2 6 10 0.4 7.6 Calibration Results: Test tube 0 1 2 3 4 5 6 7 8 9 Volume of 0.2M Sodium Concentration of Standard (mM) 0 10 20 40 60 80 100 Calibration Curve Absorbance (Au) nm 0.0189 0.0796 0.1680 0.3106 0.4904 0.6206 0.8018 0.2720 0.2697 0.2971 535.0 535.0 535.0 535.0 535.0 535.0 535.0 535.0 535.0 535.0 Data Analysis: Test Tubes 7-9 average: (0.2720+0.2697+0.2971) /3 = 0.2796 Using the formula Y=mx+c to find x to work out the concentration of the sodium salicylate: X = y-c /m = (0.2796- 0.0089) / 0.0078 = 34.7mM Using Beer lambert law, A = εlc, rearranging it to A / c * l = ε 0.2796/ (0.0347 * 1) = 8.05 m-1 cm-1 the molar absorption coefficient is 8.05 m-1 cm-1 Discussion: After conducting the experiment, the result received of the concentration of sodium salicylate was 34.7mM. The actual value for solution A was 35mM. This shows that when conducting the experiment, it was completed with minimal errors. The reason why it wasn’t exactly 35mM was due to human errors involved in the experiment. An example that could have taken place if there were any mistakes during the weighing process with the machine may have not been calibrated enough to receive the actual value. After obtaining a result very close to the actual value, it shows that my equipment was calibrated properly as the result was only 0.3mM away from the actual value of 35mM. Conclusion: After conducting the experiment, the aims for this experiment were successfully met. One of the main aims of this experiment was to be able to calculate the concentration of sodium salicylate found in face wash solutions. Comparing with the actual value of the commercial face wash solution, the results were very close to each other indicating that the aim was successfully met. The other aims were to be able to use a colorimeter accurately and to be able to create a calibration curve. This was achieved as in order to conduct the experiment; a colorimeter was required. The research conducted before the experiment helped to achieve this aim.