I believe that for the first one, should be cleaned and dry. But for the second, it does not need to be dry because we would need to condition our pipet first. Can someone explain further as to why?
Chemistry 1B Name: Experiment 6B Prelab Assignment Section Pre-Lab: Before coming to lab: Make an outline of the experimental procedures in your notebook. Before coming to lab: Prepare the following table to record your titration data into your lab notebook. As always, tables are to be neat and drawn with a straight edge. Leave room for additional titrations to be performed in case a mistake is made. Titration CaSO4 (mL) Vanal(mL) Vimitial (mL) Vtotal EDTA (mL) EDTA. EDTA 1 225.00 2 25.00 R25.00 Instructor use only: Answer the following questions and tear out the Prelab pages, place on the instructor's bench. l. Answer the following questions: a. You will pipet 25.00 mL of CaSo4 solution into an Erlenmeyer flask. Does the Erlenmeyer flask need to be dry? Explain why or why not. b. You will pipet 25.00 mL of Caso solution. Does that pipet need to be dry? Explain why or why not. 120
Calculate the concentration of the iron (II) ion in the second volumetric flask.
Experiment 2: Titrate the Vodka Sample
Lab Results
Record the following lab data in the table below. If you had to repeat one of the titrations, disregard the value that was different.
(a) volume of potassium dichromate solution added to the Erlenmeyer flask in mL
5.00ml
(b) coarse titration volume of iron (II) solution range in mL
14.10 -14.15 ml
(c) volume of iron (II) solution delivered from the burette in mL during the first fine titration
14.13ml
(d) volume of iron (II) solution delivered from the burette in mL during the second fine titration
14.11ml
(e) average volume of iron (II) solution used in the fine titrations
14.12ml
(f) the color of the analyte solution at the end point of the titration
purple
(g) the color of the analyte solution after adding the indicator
dark green
Data Analysis
Record and calculate the quantities in the table below using the data from your dichromate titrations. Use an average value for the volume of iron (II) solution used in the titration. If one of your values is very different, and you had to perform the titration three times, disregard the value that was very different when computing the average.
(a) volume of potassium dichromate solution added to the Erlenmeyer flask in mL 5.00ml
(b) moles of dichromate ion added to the Erlenmeyer flask
(c) average volume of iron (II) solution delivered from the burette in mL 14.12ml
(d) moles of iron (II) ions delivered from the burette
(e) moles of excess dichromate ions that reacted with the iron (II) ions (remember that the ratio in which they react is 1 dichromate : 6 iron (II))
(f) moles of dichromate that reacted with the ethanol in the vodka (Subtract excess dichromate ions that reacted with the iron (II) ions from the original moles of dichromate ion present.)
(g) moles of ethanol in the 5 mL diluted vodka sample according to the stoichiometric ratio of 2 dichromate ions to 3 ethanol molecules
The amount of alcohol in a drink is typically reported as percent alcohol by volume. Volume percent or volume/volume percent (% v/v) most often is used when preparing solutions of liquids. Volume percent is defined as: % v/v = Vsolute/Vsolution à 100 Find the percent alcohol (ethanol) by volume for the vodka used in the lab by following the steps outlined in the table below.
(a) given the molar mass of ethanol of 46.07 g/mol, calculate the mass of alcohol (ethanol) in the tested sample solution
(b) given the density of ethanol of 0.7893g/ml, find the volume in mL of ethanol present in the diluted vodka solution
(c) record the volume of vodka used in the experiment in mL
(d) find the percent alcohol by volume (% v/v) in the diluted vodka solution
(e) the diluted vodka solution was prepared by diluting 2.00 mL vodka to 100.00 mL. Calculate the dilution factor used (N:1)
(f) multiply the percent alcohol by volume in the diluted vodka solution by the dilution factor to obtain the % v/v alcohol in the original vodka solution
Conclusions
The Grey Moose vodka tested in this lab reports a percent alcohol by volume of 40.0% on its label. How does your value compare to the reported one? If the values are different, give one possible experimental error that might have contributed to the difference.
Potassium permanganate is another strong oxidizing substance similar to potassium dichromate. An acidic solution of purple permanganate ions can get reduced to colorless Mn2+ ions in the presence of ethanol. Write down the redox reaction between permanganate and ethanol, and balance it using the half-reaction method.
Besides vodka, there are other colorless alcohol-containing beverages that can be titrated following the procedure in your lab. Given the average values for the percent alcohol by volume listed in the table below, which beverage do you expect to use the least amount of iron (II) standard solution during the titration? Assume all lab procedures stay the same.
