Calculate pFe at each of the following points in the titration of 29.42 mL of 0.

Question

Calculate pFe at each of the following points in the titration of 29.42 mL of 0.0246 M EDTA with 0.0123 M FeCh. The EDTA solution is buffered at a pH of 10.00. The fraction of free EDTA in the Y form (any can be found here. The formation constant for the Fe2+-EDTA complex is given by log K, = 14.30. a) 5.884 ml )58.84 ml Number Number b) 23.54 mL 9) 58.96 mL Number Number c) 47.07 mL h) 64.72 mL Number Number Scroll down to view the entire question d) 57.66 ml i) 70.61 mL Previous G-ve up & Vime Scalion0 Check Answer 0 Next Exit

Explanation / Answer

a) Moles of EDTA = 0.0246 mol/lit * 0.02942 lit = 7.23732*10-4moles
moles of Fe+2 = 0.0123 mol/lit * 5.884*10-3 lit = 7.23732*10-5 moles
7.23732*10-5moles Fe+2 binds 7.23732*10-4moles of EDTA that are leaving
(7.23732*10-4 - 7.23732*10-5 ) i.e) 6.51358*10-4 moles of Fe2+ are left over
M of Fe2+ in solution =( 6.51358*10-4 moles of Fe2+) / ( 0.02942 lit + 5.884*10-3 lit )
M of Fe2+ = 0.0184499 M
PFe+2 = - log [ 0.0184499] = 1.734

b) similarly you can calculate for rest of the volumes of Fe+2
Fe+2 = 0.0123 mol//lit * 0.02354 lit = 2.89542*10-4 moles
  4.3419*10-4 moles of Fe+2 are leftover
  [Fe2+] =  4.3419*10-4 moles / (0.02942 +0.02354) lit = 8.198451*10-3 M
  PFe+2 = 2.086

c) Fe+2 = 5.78961*10-4 moles
1.53771*10-4 moles of Fe+2 are left over
2.01034*10-3M= [Fe+2]
P Fe+2 = 2.697

d) Fe+2 = 7.09218*10-4moles
   1.44771*10-4 moles are left
   [Fe2+] = 1.662505*10-3 M
   P Fe+2 = 2.78

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