Tip 1: How to make the reactions in chemistry

reaction equation - conventional post chemical process in which some substances are transformed into other with change of properties.To write the formula of chemical reactions using materials and knowledge about the chemical properties of the compounds.
correctly write the formula, according to their names.For example, aluminum oxide Al₂O₃, index 3 of aluminum (corresponding to the degree of oxidation in the compound) set near the oxygen and the index 2 (oxidation state of oxygen) near aluminum.
If the degree of oxidation of +1 or -1, the index is placed.For example, you need to write the formula of ammonium nitrate.Nitrate - acid residue of nitric acid (-NO₃, sd-1), ammonium (-NH₄, sd 1).Thus the formula of ammonium nitrate - NH₄ NO₃.Sometimes, the degree of oxidation is indicated in the title compound.Oxides of sulfur (VI) - SO₃, silicon oxide (II) SiO.Some simple substances (gases) are recorded with the index 2: Cl₂, J₂, F₂, O₂, H₂, etc.
is necessary to know what substances
react.Visible signs of reaction gas evolution, discoloration and precipitation.Very often, reactions occur without visible changes.
Example 1: neutralization
H₂SO₄ + 2 NaOH → Na₂SO₄ + 2 H₂O
sodium hydroxide reacts with sulfuric acid to form a soluble salt of sodium sulfate and water.A sodium ion is cleaved and connects with an acidic residue is substituted with hydrogen.The reaction takes place without any external signs.
Example 2: yodoformnaya sample
S₂H₅OH +4 J₂ + 6 NaOH → CHJ₃ ↓ + 5 NaJ + HCOONa + 5 H₂O
reaction proceeds in several stages.The end result - the loss of iodoform yellow crystals (qualitative response to alcohol).
Example 3:
Zn + K₂SO₄ ≠
reaction is impossible, sincein the electrochemical series of metals zinc, potassium, and after standing can not displace it from the compounds.
law of conservation of mass states: weight substances, unreacted equal weight compounds formed.Correct entry of a chemical reaction - half the battle.It is necessary to arrange the coefficients.Start equated with those compounds of formula which there are large indexes.
K₂Cr₂O₇ + 14 HCl → 2 CrCl₃ + 2 KCl + 3 Cl₂ ↑ + 7 H₂O
To place the coefficients start with potassium dichromate becausein its formula, it contains the largest index (7).
Such accuracy in recording the reactions needed to calculate the weight, volume, concentration, released energy and other variables.Be careful.Remember the common formula of acids and bases as well as acid residues.

Tip 2: How to write reaction equation

reaction is called the transformation of some chemicals in the others.A formula of recording using special characters and the equation of the reaction.There are various types of chemical interactions, but the principle of recording of the formulas is identical.
How to create a reaction equation
you need
  • periodic system of chemical elements DIMendeleev
the left side of the equation is written starting materials that react.They are called reagents.Recording is performed using special symbols that denote each substance.Between substances reagents placed "plus" sign.
the right side of the equation is written formula obtained one or more substances, which are called the reaction products.Between the left and right sides of the equation instead of the equal sign is placed arrow that indicates the direction of reaction.
After the formulas of reactants and reaction products is necessary to place the coefficients of the reaction.This is done in order to, according to the law of conservation of mass, the number of atoms of the same element in the left and right sides of the equation remains the same.
To properly arrange the factors you need to consider each of the substances reactive.To this end one of the elements is taken and compared to the number of its atoms on the left and right.If it is different, then you need to find a multiple number indicating the number of atoms of the substance in the left and right sides.This is then divided by the number of atoms of the material in the corresponding portion of the equation, and the coefficient is obtained for each of its parts.
Since the coefficient placed before the formula and applies to all substances falling into it, the next step will be to compare the obtained data with the number of other substances, leading into the formula.This is done in the same way as with the first element, and taking into account the existing rate for the entire formula.
Once dismantled all the elements of the formula, final check compliance of the left and right sides.Then the equation of the reaction can be considered complete.
The equations of chemical reactions can not be reordered left and right sides.Otherwise, you get a completely different process diagram.
Helpful Hint
number of atoms as individual substances, reagents and materials included in the products of the reaction is determined by means of the periodic table of chemical elements DIMendeleev
  • reaction equation
  • equation in chemistry