Writing my Chemistry 2 Lab Report, PLEASE HELP!! I have a few questions to answe
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Writing my Chemistry 2 Lab Report, PLEASE HELP!! I have a few questions to answer in my lab report, and I just don't fully understand what exactly I need to do. I've attached the lab handout and data that I have so far. Please write any steps that will help me understand! Thank you!!
Part 2: Determining the equilibrium constant
Table .2 shows the amounts of 2.00 ´ 10–3 M Fe(NO3)3 (in 1 M HNO3) solution, 2.00 ´ 10-3 M KSCN solution, and DI water that you should add to each tube. Add these chemicals to your three test tubes. Note that your test tubes are labeled by number. Be sure to add the solutions to the correct tube. Pipet the approximate amount of each solution into each tube. On your data sheet, record the exact amount of each solution that you add. You will need to use these actual amounts in your calculations.
Table 2 Composition of solutions for determining the equilibrium constant.
Test Tube
Vol of 2.00 ´ 10-3 M Fe(NO3)3 in 1 M HNO3 (mL)
Vol of 2.00 ´ 10-3 M KSCN (mL)
Vol of DI water
(mL)
1
5.0
1.0
4.0
2
5.0
2.0
3.0
3
5.0
3.0
2.0
4
5.0
4.0
1.0
5
5.0
5.0
0
Data and Results (length varies)
1. Include your data sheet, your Excel graph and data, and calculations in this section.
2. What differences did you see in the solutions that you prepared in Part 1?
3. You have been told that the reaction you are observing is:
Fe3+ (aq) + SCN-– (aq) ? FeSCN2+ (aq)
Another possibility is that the reaction is:
Fe3+ (aq) + 2 SCN-– (aq) ? Fe(SCN)2+ (aq)
Write the equilibrium equation for this new reaction.
Using your data from the mixtures in test tubes 1, 3, and 5 of Part 2, recalculate three new equilibrium constants for this new possible reaction. Hint: Notice that the change in concentration of SCN- in your equilibrium table will change because of the new stoichiometry. Also, the exponent on [SCN-] in the equilibrium constant expression will change for the same reason.
What are the three new equilibrium constants?
Why do the results of your calculations show that the reaction you are observing is more likely to be the first one (one mole of SCN- with one mole of Fe3+)?
4. In Part 1 of this experiment, you made the assumption that the FeSCN2+ concentrations in your standard solutions were equal to the initial concentrations of SCN- ions. Now that you know the value of the equilibrium constant, calculate the actual equilibrium concentrations of Fe3+, SCN-, and FeSCN2+ in mixture in test tube 2. How good was the assumption? Did this satisfy the 5% rule (the loss of reactant is less than 5% of its initial concentration)?
Test Tube
Vol of 2.00 ´ 10-3 M Fe(NO3)3 in 1 M HNO3 (mL)
Vol of 2.00 ´ 10-3 M KSCN (mL)
Vol of DI water
(mL)
1
5.0
1.0
4.0
2
5.0
2.0
3.0
3
5.0
3.0
2.0
4
5.0
4.0
1.0
5
5.0
5.0
0
Explanation / Answer
You need to understand the following things as you have already done all the calculations
a) The absrobance experiment is based on Lambert's Beer law which is
Absrobance = absrobpitivity X concentration X length
The absrobance will depend upon the concentration of Fe(SCN)+2 formed due to reaction between ferric ion and thiocyante ion.
so more the formation more the absrobance.
We have absrobance at different concentration of Ferric ion and thiocynate ion, so we can calculate the absrobptitivity from this.
b) The equiibrium constant = Kc = [Fe(SCN)+2] / [Fe+3][SCN-]
For second equation given
Fe3+ (aq) + 2 SCN-– (aq) Fe(SCN)2+ (aq)
The Kc = [ Fe(SCN)2+]/ [Fe+3][SCN-– ]^2
So the value of equilibrium constant will change accordingly
c) we can determine the concentration of various species from the following step
(i) moles = Molarity X volume of solution taken
Concentration after reaction = Moles left / total volume of solution.
Hope it will help you.
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