Transcript Review of Diprotic Acid Titration

Review of Diprotic Acid Titration
Analysis of 0.181g Carbonate / Bicarbonate Sample
# mol HCO3-
= (0.02630 - 0.00740 L) x (0.1000 M) x (1 mol HCO3- / 1 mol HCl)
= 0.001890 mol HCO3-
# mole CO32- = (0.00740 - 0.00060 L) x (0.1000 M) x (1 mol CO32- / 1 mol HCl)
= 0.000680 mol CO32# mole HCO3- in original mixture
= # mol HCO3- - # mol HCO3- produced in titration to Phen. End Pt.
= # mol HCO3- - # mol CO32= 0.001890 mol - 0.000680 mol = 0.001210 mol HCO3#g NaHCO3 = (0.001210 mol) x (84.007 g/mol) = 0.102 g
#g Na2CO3 = (0.000680 mol) x (105.9885 g/mol) = 0.072 g
wt% NaHCO3
= (0.102g / 0.181g) x 100 = 56.3 %
wt % Na2CO3
= (0.072g / 0.181g) x 100 = 39.8 %
Complexometric Titration
Typical Complexing Agents
EDTA
Ca-EDTA Titration
0.00 mL Titrant Added
Titration Reaction
end
EDTA
Ca2+
CaEDTA2+
=0M
= 0.00500 M
=0M
EDTA
Ca2+
CaEDTA2+
0
0.0500
0
Equilibrium Reaction
Initial
[Ca2+] = 0.00500 M
Concentration
pCa = - log(0.00500) = 2.30
25.00 mL Titrant Added (Equivalence Point)
Titration Reaction
start
end
EDTA
Ca2+
CaEDTA2+
(0.0100M)(0.02500L)
= 0.000250 mol
(0.0050M)(0.05000L)
= 0.000250 mol
= 0 mol
0 mol
0 mol
0.000250 mol
=0M
(0.000250mol)/(0.07500L)
= 0.00333M
=0M
Equilibrium Reaction
EDTA
Ca2+
CaEDAT2+
Initial
0
0
0.00333
Change
+x
+x
-x
Equilibrium
x
x
~0.00333
1.75 x 1010 = (0.00333) / x2
x = [Ca+] = 4.36 x 10-7 M
Concentration
pCa = - log(4.36 x 10-7) = 6.36
50.00 mL Titrant Added
Titration Reaction
start
end
EDTA
Ca2+
CaEDTA2+
(0.0100M)(0.05000L)
= 0.000500 mol
(0.0050M)(0.05000L)
= 0.000250 mol
= 0 mol
0.000250 mol
0 mol
0.000250 mol
(0.000250mol)/(0.1000L)
= 0.00250 M
=0M
Equilibrium Reaction
EDTA
Ca2+
CaEDAT2+
Initial
0.00250
0
0.00250
Change
+x
+x
-x
Equilibrium
~0.00250
x
~0.00250
1.75 x 1010 = (0.00250) / (0.00250) x
x = [Ca+] = 5.71 x 10-11 M
Concentration
pCa = - log(5.71 x 10-11) = 10.24
(0.000250mol)/(0.1000L)
= 0.00250M
Indicators