Final answer:
The correct answer is (d) hydronium. When a proton is added to a water molecule, it forms a hydronium ion (H3O+). The concentration of hydronium ions in a solution determines its acidity or basicity, which is measured on the pH scale.
Step-by-step explanation:
The correct answer is (d) hydronium.
When a proton is added to a water molecule, it forms a hydronium ion (H3O+). The hydronium ion is the more logical representation of a hydrogen ion in an aqueous solution, as bare protons do not exist in solution. The concentration of hydronium ions in a solution determines its acidity or basicity, which is measured on the pH scale.
In a neutral solution, the concentration of hydronium ions is equal to the concentration of hydroxide ions. An acidic solution has a higher concentration of hydronium ions, while a basic solution has a lower concentration of hydronium ions.