Question

need help completing the chart and with questions 5 and 6

7-2: Standardization of a Permanganate Solution of Titrations provide a method of quantitatively measuring the concentration of an unknown solution. This is done by delivering a titrant of known concentration into an analyte of known volume. (The concentration of an unknown titrant can also be determined by titration with an analyte of known concentration and volume.) In oxidation-reduction (redox) titrations, the voltage resulting from the mixture of an oxidant and reductant can be measured as the titration proceeds. The equivalence point of the titration, or the point where the analyte has been completely consumed by the titrant, is identified by the point where the voltage changes rapidly over a small volume of titrant delivered. In this assignment, you will determine the molarity of an unknown solution of KMnO by titrating against a primary standard, solid As 03. 1. Start Virtual ChemLab, select Electrochemistry, and then select Standardization of a Permanganate Solution from the list of assignments. The lab will open in the Titrations laboratory. 2. Click the Lab Book to open it. Click the Beakers drawer and place a beaker in the spotlight next to the balance. Click on the Balance area to zoom in, open the bottle of As Os by clicking on the lidt (Remove Lid). Drag the beaker to the balance to place it on the balance pan and tare the balance. Pick up the Scoop and scoop out some sample by first dragging the scoop to the mouth of the bottle and then pulling the scoop down the face of the bottle. As the scoop is dragged down the face of the bottle it will pick up different quantities of solid. Select the smallest sample size at the top and drag the scoop to the beaker on the balance until it snaps in place and then let go. You should have approximately 0.1 g of As2O, in the beaker. Record the mass of the sample in the data table on the following page and return to the laboratory 3. Drag the beaker from the balance to the sink and hold it under the tap to add a small amount of water. Place it on the stir plate and add the voltmeter probe to the beaker. 4. The buret will be filled with a solution of KMnO, of unknown concentration. A bottle of permanganate is on the lab bench. Record the unknown sample number. Click the Save button in the Buret Zoom View window so the titration data can be saved. The horizontal position of the orange handle is off for the stopcock. Open the stopcock by pulling down on the orange handle. The vertical position delivers solution the fastest with three intermediate rates in between. Turn the stopcock to one of the fastest positions. Observe the titration curve. When the blue line begins to tum up, double- click the stopcock to turn it off. Move the stopcock down one position to add volume drop by drop. There are two methods for determining the volume at the equivalence point: () Stop the titration when a color change occurs. Click the Stop button in the Buret Zoom View. A blue data link will appear in the lab book. Click the data link icon to open the Data Viewer window. Scroll down to the last data entry and record the volume at the equivalence point in the data table. OR (2) Add drops slowly through the equivalence point until the voltages reaches a maximum and levels off. Click the Stop button in the Buret Zoom View. A data link icon will appear in the lab book. Click the data link icon to open the Data Viewer window. Click the Copy Data button to copy and paste the data into a spreadsheet program. Plot the first derivative of voltage vs. volume. The peak will indicate the volume at the equivalence point since this is where the voltage is changing the most rapidly as the volume changes. To repeat the titration, drag the beaker to the red disposal bucket, move a few beaker from the beaker drawer next to the balance, and repeat the procedure. Do not forget to refill the buret with KMnO4 and place the voltmeter in the beaker each time.