Final Answer:
Sodium chloride salt is the best choice for a hot pack.Thus correct option is
a) Sodium chloride for hot pack, potassium chloride for cold pack
Step-by-step explanation:
Sodium chloride (NaCl) is a preferable choice for a hot pack due to its high heat capacity and its ability to retain heat for extended periods when dissolved in water. The enthalpy change (∆H) during the dissolution process of NaCl is significant, leading to the generation of heat. This characteristic makes it suitable for hot packs as it releases heat when dissolved, providing warmth.
On the other hand, potassium chloride (KCl) is well-suited for a cold pack. When dissolved in water, KCl exhibits an endothermic reaction, absorbing heat from its surroundings. This absorption of heat leads to a decrease in temperature, making it suitable for cold packs by creating a cooling effect upon dissolving.
The choice of salts for hot and cold packs depends on their specific heat capacities, enthalpy changes during dissolution, and their ability to either release or absorb heat upon dissolution. Sodium chloride's ability to release heat makes it ideal for hot packs, while potassium chloride's capacity to absorb heat makes it an excellent choice for cold packs. These characteristics are essential as they directly impact the effectiveness of the packs in generating heat or cold when activated by dissolving in water.