JAMB - Chemistry (1997 - No. 14)
A major process involved in the softening of hard water is the?
conversion of a soluble calcium salt to its trioxoncarbonate (lV)
decomposition of calcium trioxocarbonate (lV)
conversion of an insoluble calcium salts to its trioxocarbonate (lV)
oxidation of calcium atoms to its ions
Vysvetlenie
Now in permanent hardness of water, when washing soda is treated with water, the carbonate ions from sodium carbonate react with calcium and magnesium ions in water and produce an insoluble product.
Therefore, calcium carbonate is precipitated out.