Determination of concentration of Sn
2+and % of Fe
2+by Titration – Simulation
A. Objective
Using a simulation experiment carry out a titration procedure to:
• Determine the concentration of Sn2+ in aqueous solution by redox reaction with KMnO4 (aq)
• Determine the % Fe2+ in solid mixture by redox reaction with KMnO4 (aq)
B. Required software
In order to do the BeyondLabz simulation:
• Install and download the program by first going to www.beyondlabz.com/#download. o Click “purchase” and follow the instructions.
o Use the activation code SMC-STUDENT-2020
• If you are having difficulty, the following video might help:
https://www.youtube.com/watch?v=fSOitbrZoKs&feature=youtu.be • Familiarize yourself with the overall set-up of the virtual labs
• Carry out the titration experiment following the steps in the procedure below.
C. Background
Titration is a procedure commonly used to determine the concentration of one solution (analyte) by having it react with a known concentration of another solution (titrant) and measuring the volume of the titrant used to reach the end point. The end point is indicated by a change in color of the solution when the reaction is at (or very close) to the “equivalence point”. This happens when the
stoichiometrically required amount of the titrant has reacted with the amount of analyte present. Titration is commonly used to find the concentration of an unknown acid or base. However, this procedure can also be used for redox reactions or any reaction that whose equivalence point can be accurately estimated using an indicator or some other instrument.
You have already have watched video(s) of and learnt about titration procedure in a traditional laboratory setting. For this lab, you will use BeyondLabz simulation software to do the experiment virtually.
You will carry out two simulated titration experiments that illustrate the use of this procedure. In the first simulation you obtain the equipment and the reagents needed from the stockroom (Experiment
a) Experiment 1: the concentration of Sn2+ in a solution will be determined by reacting it with an
oxidizing agent, KMnO4. The equation for the redox reaction in acidic solution is shown below:
5SnCl2 +2 KMnO4 + 16 HCl 5 SnCl4 + 2 MnCl2 + 8 H2O + 2KCl
For this experiment, you will pick the required equipment from the drawers, and obtain the reagents needed from the stockroom. Note that you need to pick up the bottle labeled “Permanganate (acidic)”for KMnO4.
b) Experiment 2: the percent of Fe2+ in unknown solid mixture will be determined by reacting with
an oxidizing agent, KMnO4. The equation for the redox reaction in acidic solution is shown
below
5FeCl2 + KMnO4 + 8 HCl 5 FeCl3 + MnCl2 + KCl + 4 H2O
For this experiment, a “preset” procedure will be used in which the initial set up is already done in the simulation.
An external indicator is not needed for either of these titrations because one of the reactants, KMnO4(aq), has a strong color and the end point can be detected when it is present even in trace
amounts (which happens when the amount added starts exceeding the stoichiometric amount).
Virtual lab setup
Follow the steps below to familiarize yourself with the Titration virtual lab set-up:
• Download and install the BeyondLabz program (as described in Section B of this document, “Required Software”) if you have not done so already.
• Go to beyondlabz.com and log into the account you created previously. • Click the “Chemistry” icon and click “Install”.
• Once the installation is complete, click the “Open” button that replaced the “Install” button.
• Click on the “Titrations” icon. A virtual lab room showing basic common titration equipment (diagram shown above) will open.
• Ring the bell (located on the left side of the stockroom) for help. This will pop up a new window displaying the “Table of Content”, a list titled “Laboratories”, and an “Overview” pane.
• Click “Titrations” under “Laboratories”. A list of topics (Overview, The Simulation, The Laboratory, Transferring Solutions, Analytical Balance, Pipets, Buret and Graphing, Meters, Indicators, Saving Data, The Stockroom) will appear.
• Click each topic and read their content. The instructions here will help you carry out the experiments. However, you do not need to understand each step at first glance since you will also get step by step instruction by just following the lab procedures given below or by ringing the “help” bell in front of the stockroom when you need an explanation.
• Close (or minimize) the help window, go back to the “virtual lab room” and follow the steps listed for Experiment 1 and Experiment2
Procedure
Experiment 1: Determine the concertation of Sn2+ in a solution
1) Click on the “Titration” icon.
2) Open the stockroom at the back of the lab by clicking on it.
3) Click on the KMnO4 bottle (on the third bench second to last) and drag it to the bottom of the bench (the
bench will light up to tell you where to put it).
4) Click on “unknown” on the bottom bench. Two bottles will appear.
o at the bottom of the screen change “Acid/base” display to “potentiometric” display o on the left bottle click “select unknown” arrow
o scroll down and click on “tin(II) chloride (.0900 to 0.1100) o click on the green arrow “return the stockroom”
5) Drag the two bottles to the “stockroom shelf” (circular light will show up to show you where to put them) 6) Click on the green arrow on the top right corner “return to the lab” which will place the two bottles to the
“stockroom shelf “in the front.
7) Drag both bottles (one at a time) down to the top lab bench (circular light will show up to show you where to put them).
8) Click on the buret. A magnified view of the liquid level will appear on the left side.
9) Drag and place the KMnO4 bottle on the top of the buret. The solution will pour out and start filling the
buret. Add the KMnO4 (aq) solution until the buret fills out to 0.00 (or very close to 0). Remember:
burets are read from the top (therefore 0.00 means it is completely full with 50. mL solution). 10) Record the initial buret reading to the correct significant figure.
11) Click on “pipets” drawer in the front which will open up to show you pipets with different volumes. 12) Double Click on the 10.00 mL pipet. The pipet fitted with a pipet bulb, will then show up attached to a
stand to the left side of the buret clamp.
13) Click on the “beakers” drawer and drag one of the beakers (200 mL) to the bottom of the pipet (the surface of the bench will light up to show you where to put it)
14) Drag and place the SnCl2 bottle over the beaker and pour the solution (3 or 4 pouring sounds are
sufficient).
15) Double click on the pipette bulb and the pipet will immerse into the solution in the beaker and will draw out 10.00 mL of the solution.
16) Drag the beaker that is holding the SnCl2 solution to the right of the buret and put it on the lighted part of
the bench.
17) Drag another empty beaker from the drawer and place it under the pipet.
18) Double click on the pipet bulb which will empty all the content of the pipet into the beaker. 19) Drag the beaker and its contents and put it on the top of the stirring plate.
20) Click “plate stir switch” in front of the stirring plate to start the stirring.
21) Open the stopcock on the buret by dragging the end of its orange handle to turn it. The KMnO4 solution should start dripping out. The simulated stopcock seems to have four flowrate settings. Do not let the titrant out too fast. Otherwise you will not be able to stop at the end point.
22) Add the KMnO4 solution drop by drop until the color of the solution turns light purple.
23) Make sure to turn back the stopcock and stop the titration as soon as the solution in the beaker gains a color. Record the volume of the solution in the buret to the right number of significant figures.
24) Click on the “clean up lab bench” container located to the right of the experiment table to clean the setup and get it ready for Trial 2.
Experiment 2:Determine the percent of Fe2+ in an impure Solid: A pre-set Experiment
In this experiment you will use the “pre-set” experiment, which means some part of the procedure is already set up for you!
1) Click on the stockroom.
2) Click on the clipboard that is hanging on the right side of the stockroom. 3) Choose the “Iron Determination Unknown” (the 13th in the list).
4) In this experiment solid FeCl2 will be titrated with KMnO4.
5) A “pre-set” setup containing all the equipment and all the reagents needed will show up in the lab. 6) The buret will be filled with a known concentration of KMnO4 (molarity shown on the bottle on the left).
7) On the lab bench is shown a balance; click on the balance and it will open the balance room. 8) On the balance is shown impure FeCl2 solid on a weighing paper. Record the weight of the FeCl2.
9) Drag the weighing paper and its content to the beaker and the FeCl2 will pour into the beaker.
10) Notice the weight of the empty weighing paper reads 0.000 (this suggests that the balance was “tared” with a weighing paper on it before the addition of the FeCl2).
11) Click the green “Zoom out” arrow to return to the lab bench. 12) Drag the beaker to the top of the stirring plate.
13) The stir plate has been turned on to stir the solution.
14) Record the initial reading of the buret to the correct significant figure.
15) Slowly add the KMnO4 solution from the buret until the end point is reached (color change). Record the
final reading of the buret.
16) No external indicator is needed for this reaction since the end point is indicated by the color of excess KMnO4. Note the color of the KMnO4 solution.
