the ionisation constant of acetic acid is 1.74 × 10-⁵. calculate the degree of dissociation of acetic acid in its 0.05M solution. calculate the concentration of acetate ion in the solution and it's pH
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Answer:
The dissociation equilibrium is CH
3
COOH⇌CH
3
COO
−
+H
+
.
Let α be the degree of dissociation.
The equilibrium concentrations of CH
3
COOH,CH
3
COO
−
and H
+
are c(1−α),c(α) and c(α) respectively.
The equilibrium constant expression is K
c
=
[CH
3
COOH]
[CH
3
COO
−
][H
+
]
.
K
c
=
c(1−α)
(cα)(cα)
≈cα
2
α=
c
K
a
=
0.05
1.74×10
−5
=1.865×10
−2
[CH
3
CO
−
]=[H
+
]=cα=0.05×1.865×10
−2
=9.33×10
−4
M
pH=−log[H
+
]=−log(9.33×10
−4
)=3.03
The concentration of acetate ion and its pH are 9.33×10
−4
and 3.03 respectively.
Explanation:
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