Final answer:
Among the options provided, ammonium chloride (NH4Cl) would not act as a Brønsted-Lowry base in an aqueous solution because the ammonium ion is the conjugate acid of ammonia and tends to donate, not accept, a proton.
Step-by-step explanation:
The question of which substance can never act as a Brønsted-Lowry base in an aqueous solution concerns the acid-base behavior of various compounds. A Brønsted-Lowry base is defined as a substance that can accept a proton (H+). In the provided options, substances like sodium hydroxide (NaOH), sodium hydrogen phosphate (Na₂HPO₄), sodium phosphate (Na₃PO₄), and sodium bicarbonate (NaHCO₃) can, under the right conditions, all act as bases as they have the potential to accept a proton. However, ammonium chloride (NH₄Cl) would not act as a base in an aqueous solution since ammonium (NH₄+) is the conjugate acid of a weak base, ammonia (NH₃), and thus ammonium tends to donate a proton in water, acting as an acid, not as a base.