Calculate the unknown concentration of H 3 PO 4 based on coulometric titration d

Question

Calculate the unknown concentration of H3PO4 based on coulometric titration data: Approximately 100 mL of 0.2 M KBr(aq) used for the titration. Based on the experiment data, the average time for ten times coulometric titration of H3PO4 is 86.6 s, and each time 200 uL H3PO4 added.

(Note: Phosphoric acid has at most 3 labile protons; in order to calculate the concentration, two phosphate salts provided to help determine how many protons in H3PO4 are labile. 0.5 g K2HPO4 to make 100 mL solution and reaches to the endpoint at 9.75 s. 0.5 g KH2PO4 to make 100 mL solution and reaches to the endpoint at 15.94 s.)

Formula may be used: c = (it)/(nFV). i = 48.25 mA; F = 96485 C/mol.

Explanation / Answer

CORRECTED ANSWER

Using the given formula, c = (it)/(nFV).........(a)

i = 48.25 mA = 48.25 x 10^-3 A.

t = 86.6 s

F = 96485 C/mol

V for each time = volume of 10 times /10 = 200 micro L

n = 2

c = (48.25 x 10^-3 x 86.6) / ( 2 x 96485 x 2 x 10^-6)

Hence concentration of H3PO4 is, c = 7.217 M

Hope this helps !

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

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