If molar conductance at infinite dilution for CH _3 COO ^- and H ^+ ions are 50\ S cm ^2\ mol ^ -1 and 350\ S cm ^2\ mol ^ -1 respectively, molar conductivity of 5 10^ -2 M CH _3 COOH is 20\ S cm ^2 mol ^ -1 . What is the hydrogen ion concentration in mol/dm ^3 of CH _3 COOH ?
C. 2.5 10^ -3
Molar conductivity at infinite dilution for CH _3 COOH is given by Kohlrausch's law: _m^ = ^ ( CH _3 COO ^-) + ^ ( H ^+) _m^ = 50 + 350 = 400\ S cm ^2\ mol ^ -1 Degree of dissociation is: = _m _m^ = 20 400 = 0.05 Hydrogen ion concentration is: [ H ^+] = C = (5 10^ -2 ) 0.05 = 2.5 10^ -3 \ mol/dm ^3 Answer: 2.5 10^ -3
Related: Chemistry — Electrochemistry · All PYQ Banks