What is the Difference Between Soft and Hard Water?
Soft water refers to water that contains no or less soluble calcium and magnesium compounds. In natural water, rain and snow are soft water. Common is distilled water. Hard water refers to water containing more soluble calcium and magnesium compounds. Identification and distribution of soft and hard water.
Soft water hard water
- Method 1: Take a cup of hot water, pour in soapy water, and stir gently. Soft water appears on the water surface, while hard water appears on the water surface. The more scum, the harder the water. [1]
- The easiest way to soften hard water is to boil.
- The most commonly used in homes is boiling. In the laboratory, ion exchange is used.
- 1. Precipitation method: Treatment with lime and soda ash causes precipitation of Ca 2+ and Mg 2+ in the water. After filtration, soft water is obtained, and the manganese and iron ions can also be removed.
- 2. Water softener
- (1) Na 3 PO 4 : 3CaSO 4 + 2Na 3 PO 4 Ca 3 (PO) 4 + 3Na 2 SO 4
- (2) Sodium hexametaphosphate: Na 4 [Na 2 (P0 3 ) 6] + Ca 2 + Na 4 [Ca (P0 3 ) 6] + 2Na +
- (3) Acetic acid derivative of amine (EDTA): It forms chelate with Ca 2+ , Fe 2+ , Cu 2+ and other ions.
- 3. Ion exchange method:
- (1) Principle: A mixed gel is composed of inorganic or organic matter to form an exchanger core, surrounded by two different layers.
- An electric double layer of charge that undergoes ion exchange after water passes through.
- Cation exchanger: H + , Na + solid exchanges with Ca + , Mg 2+ ions.
- Anion exchanger: contains basic genes, which can exchange with anions in water.
- (2) Commonly used exchangers:
- a. Zeolite: hydrated sodium aluminum silicate
- Na 2 O · Z + Ca (HCO 3 ) 2 = CaO · Z + 2NaHCO 3
- Na 2 O · Z + CaSO 4 = CaO · Z + Na 2 SO 4
- b. Sulfonated coal:
- 2Na (K) + CaSO 4 = Ca (K) 2 + Na 2 SO 4
- 2H (K) + CaSO 4 = Ca (K) 2 + H 2 SO 4
- c. Ion exchange resin
- 4 Electrodialysis method:
- Using DC power as power, ions in water selectively pass through the resin exchange membrane to obtain soft water.
- 5. Magnetization method:
- When water flows through a magnetic field, the intermolecular gravity of calcium and magnesium salts is reduced, and hard scale is not easy to be produced