What compound is formed to reduce noncarbonate hardness when soda ash is added?

When soda ash (sodium carbonate) is added to water, it reacts with calcium and magnesium ions, which contribute to noncarbonate hardness (permanent hardness) in the water. The primary chemical reaction that occurs involves the precipitation of calcium and magnesium in the form of carbonates.

The addition of soda ash increases the pH of the water, leading to the conversion of dissolved calcium ions into calcium carbonate. This process reduces noncarbonate hardness because the resulting calcium carbonate precipitates out of the solution, effectively removing the hardness-causing ions from the water.

This reaction is significant in water treatment because it helps in the softening of water, making it more suitable for various applications, including drinking and industrial processes. Thus, calcium carbonate is the compound that is formed as a result of adding soda ash to reduce noncarbonate hardness.