Which of the following compounds will not have a different solubility with a change in pH?

• A. MgS
• B. CaCO3
• C. Fe(OH)3
• D. NaCl

Answer: (D)

Verified step by step guidance

1. Understand that the solubility of a compound can depend on pH if the compound contains ions that react with H\textsuperscript{+} or OH\textsuperscript{−} ions in solution, such as basic anions (like S\textsuperscript{2−}, CO\textsubscript{3}\textsuperscript{2−}, OH\textsuperscript{−}).
2. Analyze each compound: MgS contains S\textsuperscript{2−}, CaCO\textsubscript{3} contains CO\textsubscript{3}\textsuperscript{2−}, and Fe(OH)\textsubscript{3} contains OH\textsuperscript{−}. These anions can react with H\textsuperscript{+} ions, affecting solubility as pH changes.
3. Recognize that NaCl is a salt of a strong acid (HCl) and a strong base (NaOH), producing Na\textsuperscript{+} and Cl\textsuperscript{−} ions, which do not react with H\textsuperscript{+} or OH\textsuperscript{−} ions, so its solubility is independent of pH.
4. Conclude that compounds containing anions that can be protonated or deprotonated will have solubility affected by pH, while neutral salts like NaCl will not.
5. Therefore, the compound that will not have a different solubility with a change in pH is NaCl.