The correct option is C 1.9
Ka=1.8×10−5, degree of dissociation (α)
The dissociation of acetic acid is given by
CH3COOH (aq.)⇌H+ (aq.)+CH3COO− (aq.)Initial: C 0 0At equilibrium: C(1−α) Cα Cα
Ka=[CH3COO−][H+][CH3COOH]=(Cα)2C(1−α)Ka=Cα21−α1.8×10−5=0.05×α21−α
Since CH3COOH is a weak acid,
So, α<<11−α≈1
1.8×10−5=0.05×α2α=√1.8×10−50.05=√3.6×10−4α=1.9×10−2=0.019
% α=0.019×100=1.9%