Answer:
The reaction between the salt and water is endothermic
Explanation:
An endothermic reaction is one that absorbs heat from the surrounding creating a kind of coldness in the immediate environment of the reaction. The direct opposite of endothermic reaction is exothermic reaction, a reaction that dissipates heat to the immediate surrounding of the reaction.
Commercial cold packs works based on the principle of endothermic reaction. The packs are usually made up of water and ammonium nitrate salts isolated by easily breakable barriers. The dissolution of ammonium nitrate salts in water is generally endothermic.
In order to make use of the cold pack, a force needs to be applied to the pack in order to break the barrier separating the water and the ammonium salt. The water-ammonium salt mixture creates an endothermic reaction which immediately lowers the temperature of the resulting solution to about 35 F for a period of 10 to 15 minutes.
I think it would be B maybe
Soap is the sodium or potassium salt of long chain of fatty acid. Fatty acids when treated with NaOH or KOH forms Soap. This process is called as Saponification. Examples of Soap are as follow,
1. Sodium Stearate C₁₇H₃₅COONa
2. Potassium Oleate C₁₇H₃₃COOK
Reaction of Soap with MgCl₂;
When Soap is treated with MgCl₂ or CaCl₂ it forms insoluble precipitate called S.C.U.M. The reactions with MgCl₂ are as follow,
2C₁₇H₃₅COONa + MgCl₂ --------> 2C₁₇H₃₅COOMg + 2 NaCl
2C₁₇H₃₃COOK + MgCl₂ --------> 2C₁₇H₃₅COOMg + 2 KCl
These reaction are often found in hard water. And this reaction decreases the effectiveness of soap.