ITC

Thermometric Titration Simulation

Titration of a Host Analyte with a Weak Acid Guest Titrant.

Buffer (same for both titrant and analyte)
Concentration for buffer: mM
pH: or Concentration of added HCl (for pH adjustment) mM
Titrant
Concentration for guest⁺: mM     Addition volume: mL
pH: or Concentration of added HCl (for pH adjustment) mM
Analyte
Volume: mL     Sample concentration [H]_o: mM
pH: or Concentration of added NaOH (for pH adjustment) mM

Volume correction:    Variable Volume   Constant Volume (Microcal)
Titrant into Buffer subtraction:    None   Constant   Full

Equilibrium Constants and Enthalpies Guesses (Checked parameters are fit)
Water:
K₀ = K_w  =      DH₀ kcal/mol       (H₂O->H⁺+OH^-)
Buffer:
K₁ = K_a1 =      DH₁ kcal/mol
K₂ = K_a2 =      DH₂ kcal/mol
Guest Titrant:
K₃ = K_aG =      DH₃ kcal/mol
Guest Host:
K₄ = K_HG =      DH₄ kcal/mol

Titration data (step # and dH in kcal/mol):
2 -4.22192989 3 -4.01555651 4 -3.83007486 5 -3.5418126 6 -3.33654144 7 -3.18618664 8 -2.9194891 9 -2.75420608 10 -2.62335807 11 -2.4034328 12 -2.31122461 13 -2.07545974 14 -2.02322371 15 -1.86769248 16 -1.7537503 17 -1.607136 18 -1.56425492 19 -1.42776427 20 -1.40182929 21 -1.313118 22 -1.20162392 23 -1.15172561 24 -1.08465718 25 -1.03031828 26 -0.96689713 27 -0.91306958 28 -0.87944441 29 -0.8227212
Fit Convergence Mode: Fast Damped Strongly Damped

Titration Curve:

You can copy and paste the results into Excel for convenient plotting.

Acid Disscociation: MH2+2 = MH+ + H+ , K_aG
Association: MH2+2 + C-8 = [MH2C-6] , K_assoc
The input dH values are the enthalpy of reaction for the reactions as written above.
DH₀ = -DH(H⁺) where DH(H⁺) is the enthalpy of neutralization for protons (i.e. strong acids). DH(H⁺)=-55.81 kJ/mol is the value at infinite dilution.
The enthalpy of dilution of the titrant is not included in these calculations.
The enthalpy of dilution of NaCl is not included in these calculations.
Activity coefficients are neglected.
The output G/H column is moles(G)/moles(H).
The output dH values are per mol of titrant added.

Colby College Chemistry, Thomas W. Shattuck, 10/10/07