Final answer:
The compound PO₄³⁻has the highest concentration of hydroxide ions as it can act as a Brønsted-Lowry base, generating OH- ions when it accepts protons in solution. Hence, the correct answer is A) PO₄³⁻
Step-by-step explanation:
The question asks which aqueous solution has the highest concentration of hydroxide ions. To determine this, we can look at the compounds provided and consider their ability to either donate or accept protons in accordance with the Brønsted-Lowry acid-base theory.
From the given options, PO₄³⁻ is the compound most likely to increase the concentration of hydroxide ions in a solution since it's a base capable of accepting protons and generating hydroxide ions as it does so.
Looking at other statements from various exercises, we see that HPO42- accepts a proton from water to form H₂PO₄ and OH-. The others, such as NH4+, HCO3-, and H₂CO₃, are not as strongly basic and is largely expected to add hydronium ions to the solution rather than hydroxide ions. Hence, the correct answer is A) PO₄³⁻.