A major factor considered in selecting a suitable method for preparing a simple salt is its

Analysis

The question asks for the primary criterion used to decide how to prepare a simple salt in the laboratory. In chemistry, the preparation method (e.g., titration, precipitation, or reaction of an acid with a metal/base) depends heavily on whether the salt can dissolve in water or if it exists as an insoluble solid.

Concept Explanation

The preparation of salts is governed by their solubility rules.

1. Soluble Salts: If a salt is soluble in water, we often use methods like titration (for neutralization) or the reaction of an acid with a metal, metal oxide, or metal carbonate.
2. Insoluble Salts: If a salt is insoluble in water, it is typically prepared by precipitation (double decomposition), where two soluble salt solutions are mixed to form the insoluble salt as a precipitate.

Because the physical state of the salt in water determines the separation technique (like filtration vs. evaporation), solubility is the most critical factor.

Step-by-Step Solution

• Step 1: Evaluate the options. Melting point (B) and crystalline form (A) are physical properties, but they do not dictate the chemical synthesis route. Reactivity with acids (C) is a property of the reactants, not the salt being formed.
• Step 2: Consider the preparation of a salt like Barium Sulphate ($BaSO_4$). Since it is insoluble, we must use precipitation. Consider a salt like Sodium Chloride ($NaCl$). Since it is soluble, we use titration or evaporation.
• Step 3: Conclude that the decision to use filtration (for insoluble salts) or evaporation/crystallization (for soluble salts) is entirely dependent on the solubility of the salt in water.

Conclusion

This aligns with standard chemistry principles taught in the Nigerian secondary school curriculum, where solubility is the primary guide for salt preparation methods.

Exam Tip

Remember the "Solubility Rule" mnemonic: "All Nitrates are soluble; all Sodium, Potassium, and Ammonium salts are soluble." If you are asked about salt preparation in an exam, always check if the salt is soluble or insoluble first—that will lead you to the correct method immediately!