Florida Drinking Water Operator "B" Practice Test

The process of lime softening is primarily aimed at reducing hardness in water by using lime (calcium hydroxide) as a reagent. One of the key reactions in this process involves the precipitation of calcium carbonate (CaCO3), which is an essential goal as it helps remove hardness-causing compounds.

In the reaction where calcium bicarbonate (Ca(HCO3)2) is treated with calcium hydroxide (Ca(OH)2), the calcium ions from both compounds serve as a source for the calcium carbonate precipitate. This reaction results in the production of calcium carbonate, along with water, signifying that the bicarbonate ions react with hydroxide ions to form carbonate ions, which then combine with calcium ions to precipitate out as CaCO3.

The process contributes to both softening the water and removing excess carbonate hardness, making option B the correct choice. This reaction is prevalent in conventional lime softening operations as it effectively reduces the total hardness of the water.

Other provided options either result in the formation of compounds that do not include a significant calcium carbonate precipitate or do not correctly reflect the reactions occurring in lime softening. For instance, one of the options might misrepresent the products formed from the mixing of reactants, while others