As an expert sommelier and brewer, I can tell you that the reaction of quick lime (CaO) with water to form lime water (Ca(OH)2) is indeed an example of a combination reaction. In this reaction, the quick lime combines with water to produce calcium hydroxide, also known as lime water.
Now, let's talk about the nature of this reaction. When a reaction is described as exothermic, it means that it releases heat or energy to the surroundings. In the case of the reaction between quick lime and water, it is indeed exothermic. This means that heat is given off during the reaction.
To better understand this, let me share a personal experience. In the brewing process, we sometimes use lime water to adjust the pH of the mash or the brewing water. When we add quick lime to water, we can actually feel the heat being generated. It's a noticeable warmth that can be felt when you touch the container or the solution. This is a clear indication that the reaction between quick lime and water is exothermic.
To put it in simpler terms, the formation of lime water involves the breaking of chemical bonds in quick lime and the formation of new bonds in calcium hydroxide. This process releases energy in the form of heat. The heat generated during the reaction can be attributed to the strong ionic bond formation between calcium and hydroxide ions.
In addition to the heat released, the reaction between quick lime and water also results in the formation of a white, milky substance known as lime water. This milky appearance is due to the insolubility of calcium hydroxide in water. The formation of this milky precipitate is another characteristic of the combination reaction between quick lime and water.
To summarize, the reaction of quick lime with water to form lime water is a combination reaction, as it involves the combination of two substances to form a new compound. This reaction is exothermic, releasing heat to the surroundings. The heat generated can be felt and is often used as an indicator of the reaction taking place.