A quantitative relationship of mass dependent interaction between surface hydroxyl groups of silica and homologous series of adsorbed molecules, ΔνOH₁ - ΔνOH_X = 1/2C·ln(m_x/m₁), was derived from collision theory and Hammett σ substituent constants. This relationship was in good agreement with the results reported in literatures in either adsorption at liquid/solid interface or at vapor/solid interface and the adsorption mechanism could be characterized from the slopes of the equation by plotting the value of ΔνOH₁ - ΔνOH_X against ln(m_x/m₁). Also, good correlation between pKa and ΔνOH₁ - ΔνOH_X was confirmed as peal pKa₁ - pKa_x = -σ/f·s(ΔνOH₁ - ΔνOH_X) and pKa₁ - pKa_x = 1/2 s·log(m₁ /m_x).

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