Biology - Biotechnology and Its Applications Question with Solution | TestHub

Gluconic acid reacts with calcium to form calcium gluconate, which is highly soluble in water. It is widely used in medicine as a calcium supplement to treat calcium deficiency (hypocalcemia) because of its high solubility and bioavailability compared to other calcium salts.

Thus, gluconic acid is used in medicine for the solubility of ${\text{Ca}}^{2+}$ ions.

Answer: ${\text{Ca}}^{2+}$