. Prepare a spreadsheet to calculate and plot the theoretical titration curve fo

Question

. Prepare a spreadsheet to calculate and plot the theoretical titration curve for sample ‘e’. Assume a closed system using the reagent and titrant concentrations, initial and added volumes. Plot the measured titration curve and the calculated theoretical titration curve on the same axes. Comment on the reason for any differences. Sample e is 3 mL 1M NaOH and 4 mL 1M NaHCO3 added to freshly deionized water to 1 L (initial condition [HCO3-] = 1 x 10-3 M; [CO32-] = 3 x 10-3 M).

(just assume the Measured one )

Explanation / Answer

Initial pH

initial [HCO3-] = 1 x 10^-3 M

initial [CO3^2-] = 3 x 10^-3 M

pKa = 10.33

using hendersen-hasselbalck equation,

pH = pKa + log(CO3^2-/HCO3-)

     = 10.33 + log(3 x 10^-3/1 x 10^-3)

     = 10.81

after NaOH added = 1 M x 0.003 L = 0.003 mol

and,

added NaHCO3 = 1 M x 0.004 L = 0.004 mol

final [HCO3-] = 1 x 10^-3 M x 1 L - 0.003 mol + 0.004 mol = 0.002 mol

final [CO3^2-] = 3 x 10^-3 M x 1 L + 0.003 mol - 0.004 mol = 0.002 mol

new pH,

pH = pKa + log(CO3^2-/HCO3-)

     = 10.33 + log(2 x 10^-3/2 x 10^-3)

     = 10.33

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.