Two weak acid solutions HA1 and HA2 each with the same concentration and having pKa values 3 and 5 are placed in contact with hydrogen electrodes (1 atm, 25°C) and are interconnected through a salt br

Question

Two weak acid solutions HA1 and HA2 each with the same concentration and having pKa values 3 and 5 are placed in contact with hydrogen electrodes (1 atm, 25°C) and are interconnected through a salt bridge. EMF of the cell is

Prashant Kotian · Accepted Answer

Correct answer: D. Since HA1 is a stronger acid (pKa=3), its [H^+] will be higher, acting as the cathode. HA2 (pKa=5) will act as the anode. For a weak acid, [H^+] = √(Ka * C). The ratio [H^+]_cathode / [H^+]_anode = √(Ka1 / Ka2) = √(10^-3 / 10^-5) = √100 = 10. The cell EMF = 0.0591 * log([H^+]_cathode / [H^+]_anode) = 0.0591 * log(10) = 0.059 V. Therefore, correct answer is D.

💡 Solution & Explanation

Practice 22,000+ questions like this