Consider the titrtation of 25.0mL of 0.0100M Sn2+ by 0.0500M TI3+ in 1 M HCL, using Pt and Saturated Calomel Electrodes to find the endpoint.
F=96486.7 Cmol
E0 Sn4+/Sn2+ =0.15V
E0 TI3+/TI+ = 1.28
Esce = 0.241V
R=8.3141 J K Mol
(a) Write the balanced reaction.
Sn4+ + 2e- <--> Sn2+
TI3+ <--> TI+ + 2e-
Sn2+ + Tl3+- -> Sn4+ + Tl+
(b) Write two different half reactions for the net cell reaction.
I'm assuming this means
Sn4+ + 2e- <--> Sn2+ E0= 0.15V
TI3+ <--> TI+ + 2e- E0= 1.28 V
(c) Write the two nernst equations for the net cell reaction
Prior to the equivalence point, the equation would be;
E=1.28+RT/F ln(TI3+/TI+)-SCE (0.241)
Where TI3+/TI+ = Conc. products/reactants.
After the equivalence point, reaction then becomes,
E=0.15 + RT/F ln(Sn4+/Sn2+) - SCE
(D) calculate E at the following volumes of TI3+ : 1.00mL, 2.50mL, 4.90mL, 5.00mL,5.10mL and 10.0mL
This is the section I am having difficulty with, if anyone could help, thanks.
To calculate E at different volumes of TI3+ in the titration, we need to use the Nernst equation:
E = E° + (RT / nF) * ln(Q)
where E is the cell potential, E° is the standard cell potential, R is the gas constant (8.3141 J K^(-1) mol^(-1)), T is the temperature in Kelvin, n is the number of electrons transferred in the balanced equation, F is Faraday's constant (96486.7 C/mol), and Q is the reaction quotient.
For the half-reaction Sn4+ + 2e- <--> Sn2+, n = 2 and E° = 0.15 V.
For the half-reaction TI3+ <--> TI+ + 2e-, n = 2 and E° = 1.28 V.
At the equivalence point, all of the Sn2+ will react with TI3+, so the concentration of Sn2+ will be zero and Q will be zero. Therefore, E = E°.
Prior to the equivalence point:
E = 1.28 + ((RT) / (2F)) * ln(TI3+/TI+) - SCE
After the equivalence point:
E = 0.15 + ((RT) / (2F)) * ln(Sn4+/Sn2+) - SCE
Now we can calculate E at different volumes of TI3+. Let's assume the temperature is constant and equal to room temperature (298 K).
For the given volumes (1.00 mL, 2.50 mL, 4.90 mL, 5.00 mL, 5.10 mL, 10.0 mL), we need to calculate the concentrations of TI3+ and TI+ using the balanced reaction and the initial concentrations.
At each volume, calculate Q = [TI+]^2 / [TI3+].
Substitute the values in the Nernst equation and calculate E for each volume using the given values of E°, R, F, and SCE.
For example, at 1.00 mL:
- Calculate the concentrations of TI3+ and TI+ using the balanced reaction and initial concentrations.
- Calculate Q.
- Substitute the values in the Nernst equation and calculate E.
Repeat the same steps for other volumes to calculate E at each volume.
To calculate E at different volumes of TI3+, we need to use the Nernst equation. The Nernst equation relates the electrode potential (E) with the concentration of reactants and products in the electrochemical cell.
For the pre-equivalence point E values, we use the following equation:
E = E0 + (RT / F) * ln([TI3+] / [TI+]) - Esce
where:
E0 is the standard electrode potential,
R is the gas constant (8.3141 J K^-1 mol^-1),
T is the temperature (in Kelvin),
F is Faraday's constant (96486.7 C mol^-1),
[TI3+] is the concentration of TI3+,
[TI+] is the concentration of TI+,
and Esce is the reference electrode potential.
(a) At 1.00 mL of TI3+:
Using the given concentrations and values, we can substitute them into the equation:
E = 1.28 + (8.3141 * T / 96486.7) * ln(0.0500 / [TI+]) - 0.241
(b) At 2.50 mL of TI3+:
Again, we substitute the given concentrations and values into the equation:
E = 1.28 + (8.3141 * T / 96486.7) * ln(0.0500 / [TI+]) - 0.241
(c) At 4.90 mL of TI3+:
E = 1.28 + (8.3141 * T / 96486.7) * ln(0.0500 / [TI+]) - 0.241
(d) At 5.00 mL of TI3+:
E = 0.15 + (8.3141 * T / 96486.7) * ln([Sn4+] / [Sn2+]) - 0.241
(e) At 5.10 mL of TI3+:
E = 0.15 + (8.3141 * T / 96486.7) * ln([Sn4+] / [Sn2+]) - 0.241
(f) At 10.0 mL of TI3+:
E = 0.15 + (8.3141 * T / 96486.7) * ln([Sn4+] / [Sn2+]) - 0.241
Substitute the appropriate concentrations of TI3+ and TI+ for each volume into the equations to calculate the respective E values. Remember to use the proper value for Esce and the given values for E0.