Final answer:
K₃PO₄ is the strongest electrolyte on the list as it produces the greatest number of ions upon complete dissociation, with a total of four ions (3K⁺ and PO₄³⁻) in solution.
Step-by-step explanation:
Assuming 1 mole of each compound in the list completely dissociates, the strongest electrolyte is determined by the substance that produces the most ions in solution. Strong electrolytes dissociate completely into ions in solution, contributing to their ability to conduct electricity. Substances like sodium chloride (NaCl) are strong electrolytes. Comparing the given compounds, NaCl, CaSO₄, K₃PO₄, NH₄Br, and CO₂, we need to consider the total number of ions produced upon dissociation. NaCl dissociates into 2 ions (Na⁺ and Cl⁻), CaSO₄ into 3 ions (Ca²⁺ and SO₄²⁻), K₃PO₄ into 4 ions (3K⁺ and PO₄³⁻), NH₄Br into 2 ions (NH₄⁺ and Br⁻), and CO₂ does not dissociate into ions as it is a non-electrolyte. Therefore, K₃PO₄ will produce the greatest number of ions (four) upon complete dissociation, making it the strongest electrolyte among the listed compounds.