Phosphoric Acid Titration Curve
November 3, 2015

A.) Research Question
1. What is the exact initial concentration of the H
3
PO
4
solution?
2. What are pK
a1
&pK
a2
for H
3
PO
4
?
3. What are K
a1
&K
a2
for H
3
PO
4
?
4.What is the H
3
PO
4
concentration in my soft drink?
B.) Observations and Results
Table 1: Phosphoric Acid Titration Data and Concentration Results.
[NaOH]
(M)
Equiv.
Point
pH at
equiv.
Point
NaOH vol to
reach equiv
point. (mL)
NaOH
moles
(mol)
H
3
PO
4
Moles
(mol)
Starting
[H
3
PO
4
]
(M)
Average
[H
3
PO
4
]
(M)
0.099
1st
4.36
12
1.188
0.0373
0.306
0.0533
0.099
2nd
8.34
21
2.079
0.0693
0.306
Table 2: Phosphoric Acid Equilibrium Constants
Equil #
pK
a
K
a
1
1.85
1.4*10^-2
2
6.97
1.07*10^-7
Table 3: Cola Soft Drink Titration Data and Concentration Results for Sodastream
Dr.Pete
[NaOH]
(M)
Equiv.
Point
pH at
equiv.
Point
NaOH vol to
reach equiv
point. (mL)
NaOH
moles
(mol)
H
3
PO
4
Moles
(mol)
Starting
[H
3
PO
4
]in this
cola
(M)
Average
[H
3
PO
4
]
(M)
0.0495
1st
4.75
2
0.099
0.0025
0.408
0.00754
0.0495
2nd
8.82
4
0.198
0.005
0.408
-Graphs attached separately
Calculations:

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- Fall '11
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- Chemistry, pH, Pk, Equivalence point, Phosphoric acid, Equiv. pH