Answer is: the acid dissociation constant for weak acid is 0.0132.
Chemical reaction: HA(aq) ⇄ A⁻(aq) + H⁺(aq).
c(weak acid) = 0,740 M.
α(weak acid)= 12,5% ÷ 100% = 0,125.
Ka = α² · c / 1 - α.
Ka = 0,125² · 0,740 M / 1 - 0,125.
Ka = 0,0132 M = 1,32·10⁻² M.
Ka is the acid
dissociation constant, which quantifies the extent of acid dissociation (in
this example HA) in water.
