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Question:

When 0.05M dimethyl amine is dissolved in 0.1M NaOH solution, then the percentage dissociation of dimethyl amine is?

5×10⁻¹

5×10⁻⁵

5×10⁻³

5×10⁻²

Solution:

Correct option is C. 5×10⁻¹
0.05M dimethyl amine (weak base), Kb = 5×10⁻⁴
0.1M NaOH (OH⁻) = 0.1 + 0.05α ≈ 0.1
Kb = [Cα][OH⁻] / [C - Cα]
5×10⁻⁴ = α × 0.1 / 1 - α
α = 5×10⁻³