Final answer:
The least soluble salt among Ca(NO3)2, CaSO4, NaCl, and NH4NO3 is typically CaSO4, identified by its lower solubility product.
Step-by-step explanation:
The question revolves around comparing the solubility products (Ksp) of different salts to determine which one has the lowest Ksp, indicating the least soluble salt. To answer this question, one would need to consult solubility product tables or reliable data sources as the Ksp values are experimentally determined.
Given the salts mentioned: Ca(NO3)2, CaSO4, NaCl, and NH4NO3, we usually find that CaSO4 has a lower solubility product compared to the nitrates and chlorides, which are generally quite soluble. This would make CaSO4 the correct answer, as it would be the least soluble salt of the options provided assuming standard conditions.
To provide an accurate response, one must confirm the solubility product values from reputable sources focusing on the solubility equilibria for these compounds under specific conditions.