Constants |Periodic Table â¼ Part A Consider the following reaction: Fe3+ (aq) + SCN-(aq) ê·¼ FeSCN2+ (aq) A solution is made containing an initial Fe3 of 1.0x10-3 M and an initial SCN] of 7.9x104M At equilibrium, | FeSCN2+ 1.6Ã10-4 M Calculate the value of the equilibrium constant (K) Express your answer using two significant figures. K.= 203 Submit Previous Answers Request Answer X Incorrect; Try Again; 4 attempts remaining
3. You have been told that the reaction you are observing is:
Fe3+ (aq) + SCN-â (aq) â FeSCN2+ (aq)
Another possibility is that the reaction is:
Fe3+ (aq) + 2 SCN-â (aq) â 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)?
Calculate the equilibrium constant for each of the reactions at 25âC.
Standard Electrode Potentials at 25 âC
Reduction Half-Reaction
Eâ(V)
Fe3+(aq)+3eâ
âFe(s)
-0.036
Pb2+(aq)+2eâ
âPb(s)
-0.13
Ni2+(aq)+2eâ
âNi(s)
-0.23
O2(g)+2H2O(l)+4eâ
â4OHâ(aq)
0.40
Cl2(g)+2eâ
â2Clâ
1.36
I2(s)+2eâ
â2Iâ
0.54
Part A
2Fe3+(aq)+3Pb(s)â2Fe(s)+3Pb2+(aq)
Express your answer using two significant figures.
K =
Incorrect; Try Again; 4 attempts remaining
Part B
O2(g)+2H2O(l)+2Ni(s)â4OHâ(aq)+2Ni2+(aq)
Express your answer using two significant figures.
K =
Part C
Cl2(g)+2Iâ(aq)â2Clâ(aq)+I2(s)
Express your answer using two significant figures.