Which of the following compounds would increase the pH of solution?

• A. SrBr₂
• B. K
• C. NaN₃
• D. NiBr₂
• E. Hg₂Cl₂

Answer: (C)

Verified step by step guidance

1. Identify the nature of each compound in terms of their ions and how these ions affect the pH of the solution. Remember, pH increases if the solution becomes more basic (more OH⁻ ions) and decreases if it becomes more acidic (more H⁺ ions).
2. For ionic compounds, consider the hydrolysis of their ions in water. Salts derived from strong acids and strong bases generally do not affect pH, while salts containing conjugate bases of weak acids can increase pH by producing OH⁻ ions.
3. Analyze each compound: SrBr₂ dissociates into Sr²⁺ and Br⁻; both come from strong acid/base and typically do not affect pH significantly. K (potassium metal) reacts with water to produce K⁺ and OH⁻, increasing pH, but elemental K is not a salt.
4. NaN₃ dissociates into Na⁺ and N₃⁻ ions. Na⁺ is a neutral ion (from strong base NaOH), but N₃⁻ is the conjugate base of hydrazoic acid (HN₃), a weak acid. Therefore, N₃⁻ can hydrolyze to produce OH⁻, increasing the pH.
5. NiBr₂ and Hg₂Cl₂ contain metal ions that can hydrolyze to produce acidic solutions or have negligible effect on pH. Thus, among the options, the salt containing the conjugate base of a weak acid (NaN₃) is the one that increases the pH.