What is Na2S2O7? Important knowledge about Na2S2O7.

1. Definition of Na₂S₂O₇
   Na₂S₂O₇, also known as disodium disulfate or sodium metabisulfite, is a complex chemical compound of an organic nature. Its chemical formula is Na₂S₂O₇. In English, it is also referred to as Sodium Metabisulfite. Its atomic mass is 222.14 g/mol. It consists of two sodium (Na) atoms, two sulfur (S) atoms, and seven oxygen (O) atoms.

2. Properties: Na₂S₂O₇
   Na₂S₂O₇ is a fine white powder that is colorless and odorless. Its pH range is from 4.0 to 4.6 when in a 5% solution at 25°C. The main chemical property of Na₂S₂O₇ is its ability to react with most acids, metals and many other substances, producing various different products.

3. Common chemical equations of Na₂S₂O₇
   Na₂S₂O₇ reacts with metals, acids, salts and non-metals to produce unique products. Some commonly encountered chemical equations include:

• Reaction with acid: Na₂S₂O₇ + 2HCl -> 2NaCl + H₂O + 2SO₂
• Reaction with metal: 2Na₂S₂O₇ + Cu -> 4NaSO₄ + CuS
• Reaction with salt: Na₂S₂O₇ + 2NaCl -> 2Na₂SO₄ + Cl₂

4. Preparation of Na₂S₂O₇
   Na₂S₂O₇ is usually prepared in the laboratory or industrially by heating a solution of sodium bisulfite (NaHSO₃) or sodium sulfite (Na₂SO₃) with sulfur until it begins to decompose.

4.1 Laboratory preparation of Na₂S₂O₇: Na₂SO₃ + S -> Na₂S₂O₇
4.2 Industrial preparation of Na₂S₂O₇: 2NaHSO₃ → Na₂S₂O₇ + H₂O ->