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Question
The dissociation constant (Ka) and percent of degree of dissociation (α) of a weak monobasic acid solution of 0.1 M with a pH = 4, are ____________ respectively.
Options
10−7, 0.1
10−9, 0.1
10−7, 0.01
10−5, 0.01
MCQ
Fill in the Blanks
Solution
The dissociation constant (Ka) and percent of degree of dissociation (α) of a weak monobasic acid solution of 0.1 M with a pH = 4, are 10−7, 0.1 respectively.
Explanation:
pH = −log[H+]
∴ [H+] = antilog (−pH)
= antilog (−4)
[H+] = 1 × 10−4 M
A weak monobasic acid (HA) dissociates as,
\[\ce{HA_{(aq)} ⇌ H^+_{( aq)} + A^-_{( aq)}}\]
∴ [H+] = α c
∴ α = `(["H"^+])/"c" = (1 xx 10^-4)/0.1` = 1 × 10−3
∴ Percent of degree of dissociation
= α × 100
= 1 × 10−3 × 100
= 0.1%
Ka = α2c
= (1 × 10−3)2 × 0.1
= 1 × 10−7
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Types of Electrolyte
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