See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: pKa is inversely related to acid strength. A lower pKa means a stronger acid (more stable conjugate base / better ability to donate a proton). Step 1: Identify the three compounds. - (x) CH3SO3H: methanesulfonic acid (a sulfonic acid) - (y) CH3COOH: acetic acid (a carboxylic acid) - (z) CH3OH: methanol (an alcohol) Step 2: Determine relative acid strengths. - Sulfonic acids (x) are among the strongest organic acids because sulfur in the +5 oxidation state with two S=O bonds highly stabilizes the negative charge on the conjugate base (CH3SO3−) through extensive delocalization across three oxygen atoms. pKa ≈ −1 to 0. - Carboxylic acids (y) are moderately strong organic acids. The conjugate base (CH3COO−) is stabilized by resonance across two oxygen atoms. pKa ≈ 4.75. - Alcohols (z) are very weak acids. The conjugate base (CH3O−) has no resonance stabilization. pKa ≈ 15.5. Step 3: Rank by increasing pKa (weakest acid last = highest pKa). - Strongest acid → lowest pKa: (x) methanesulfonic acid (pKa ~ −1) - Middle: (y) acetic acid (pKa ~ 4.75) - Weakest acid → highest pKa: (z) methanol (pKa ~ 15.5) So increasing order of pKa: x < y < z Step 4: Check other options. - (a) y < x < z: incorrect, places acetic acid below sulfonic acid. - (c) y < z < x: incorrect, places methanol below sulfonic acid. - (d) x < z < y: incorrect, places methanol below acetic acid. Only option (b) x < y < z correctly reflects the increasing pKa order. Therefore, the correct answer is B.