Carbonic acid has pKa1 of about 6.4. Which of the following acids liberate CO2 when added to aqueous NaHCO3? (pKa: ethanoic acid 4.76, phenol 10.0, trichloroethanoic acid 0.65, p-methoxybenzoic acid 4.47)

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3co220

Carbonic acid has pKa1 of about 6.4. Which of the following acids liberate $CO X_{2}$ when added to aqueous $NaHCO X_{3}$ ? (pKa: ethanoic acid 4.76, phenol 10.0, trichloroethanoic acid 0.65, p-methoxybenzoic acid 4.47)

An acid releases

CO X_{2}

from bicarbonate when it is a stronger acid than

H X_{2} CO X_{3}

, i.e. pKa below 6.4. Ethanoic acid (4.76), trichloroethanoic acid (0.65) and p-methoxybenzoic acid (4.47) qualify, but phenol (10.0) does not.