The reaction equation - conditional record of chemical process at which some substances turn into others with change of properties. For record of chemical reactions use formulas of substances and knowledge of chemical properties of connections.
Instruction
1. Correctly write formulas, according to their names. For example, Al₂O aluminum oxide ₃, put index 3 from aluminum (corresponds to its oxidation level in this connection) near oxygen, and index 2 (oxygen oxidation level) near aluminum. If the oxidation level +1 or-1, then the index is not put. For example, you need to write down an ammonium nitrate formula. Nitrate – acid residue of nitric acid (-NO ₃, the village of the lake-1), ammonium (-NH ₄, the village of the lake +1). Thus an ammonium nitrate formula - NH ₄ NO ₃. Sometimes oxidation level is specified in the name of connection. Oxide of sulfur (VI) is SO ₃, oxide of SiO silicon (II). Some simple substances (gases) register with index 2: Cl ₂, J ₂, F ₂, O ₂, H ₂, etc.
2. It is necessary to know what substances react. Visible signs of reaction: liberation of gas, change of coloring and loss of a deposit. Very often reactions take place without visible changes. Example 1: reaction neytralizatsiiHSO ₄ + 2 NaOH → Na₂SO ₄ + 2 NOGidroksid sodium reacts with sulfuric acid with formation of soluble salt of sulfate of sodium and water. The ion of sodium is chipped off and connects to the acid rest, replacing hydrogen. Reaction takes place without external signs. Example 2: yodoformny test CHOH + 4 J ₂ + 6 NaOH→CHJ ₃↓ + 5 NaJ + HCOONa + 5 NOReaktsiya goes to several stages. The end result – loss of crystals of an iodoform of yellow color (high-quality reaction to alcohols). Example 3: Zn + ₄ ≠ Reaction is impossible K₂SO since among tension of metals zinc costs after potassium and cannot force out it from connections.
3. The mass conservation law says: the mass of the substances which reacted is equal to the mass of the formed substances. Competent record of chemical reaction – a half of success. It is necessary to place coefficients. Begin to equalize with those connections at which formulas there are big indexes. K₂Cr₂O ₇ + 14 HCl → 2 CrCl ₃ + 2 KCl + 3 Cl ₂↑ + 7 H₂O begin to Place coefficients from potassium bichromate since its formula contains the greatest index (7). Such accuracy in record of reactions is necessary for calculation of weight, volume, concentration, the emitted energy and other sizes. Be attentive. Remember the most often found formulas of acids and the bases and also the acid remains.