A major process involved in the softening of hard water is the?

The process involved in the softening of hard water is the conversion of a soluble calcium salt to its trioxocarbonate (IV) through a chemical reaction known as precipitation. Hard water is water that contains high levels of dissolved calcium and magnesium ions. These ions react with soap, making it difficult to lather and causing scale buildup in pipes and appliances. To soften hard water, we need to remove the calcium and magnesium ions from the water. One way to do this is through precipitation. In this process, we add a chemical called a precipitating agent to the hard water. The precipitating agent reacts with the calcium ions, causing them to form a solid precipitate of calcium trioxocarbonate (IV), which can be filtered out of the water. The equation for the reaction is: Ca2+ (aq) + CO32- (aq) → CaCO3 (s) where Ca2+ represents the calcium ions in the water, CO32- represents the carbonate ions in the precipitating agent, and CaCO3 represents the solid precipitate of calcium trioxocarbonate (IV). Once the calcium and magnesium ions have been removed from the water, it is considered soft and is less likely to cause scale buildup in pipes and appliances. Therefore, the correct answer is option (i): conversion of a soluble calcium salt to its trioxocarbonate (IV).