Name the sodi compound which is used for softening hard water?

The sodium compound commonly used for softening hard water is sodium carbonate, also known as soda ash. It works by precipitating calcium and magnesium ions, which are responsible for water hardness, thus reducing their concentration in the water. Another compound used for this purpose is sodium zeolite, which exchanges sodium ions for hardness-causing ions. Both methods effectively help to soften water for various applications.