Question

Phthalic acid is a diprotic acid having the formula HO2CC6H4CO2H that can be converted to a salt by reaction with base. Which of the following is expected to be most soluble in water? A) HO2CC6H4CO2H B) HO2CC6H4CO2Na C) HO2CC6H4CO2K D) NaO2CC6H4CO2Kand why?

Answer 1

Answer:

D) NaO2CC6H4CO2K

Explanation:

Water is a polar solvent and tends to solvate polar molecules. This allows solute molecules to interact with the solvent and that is why the solubility of a molecule in water increases with the increase in its polarity. So, the salt of phthalic acid is more soluble in water than phthalic acid itself. Although the monosodium and monopotassium salts are also more soluble than phthalic acid, the dialkali phthalate salt (NaO2CC6H4CO2K) is the most soluble due to the highest polarity.