Such chemical reactions during which oxidation levels at the elements which are a part of initial substances and products change are called oxidation-reduction. The solution of the equation of oxidation-reduction reactions, first of all, depends on an objective.
Instruction
1. The question sounds thus: what of the listed reactions are oxidation-reduction? Na2SO4 + BaCl2 = 2NaCl + BaSO4Zn + 2HCl = ZnCl2 + H2 the Decision on a sample of the above-stated examples comes down to the fact that over each element in the left and right parts of reactions extents of its oxidation are affixed. Those reactions where these degrees changed, and are oxidation-reduction.
2. The task can sound so: it is required to balance by method of electronic balance the equation of oxidation-reduction reaction. For an example, take already used hydrogen replacement reaction by zinc when salt of chloride of zinc and gaseous hydrogen was as a result formed.
3. It is easily possible to see that during this reaction of oxidation level zinc and hydrogen changed, and it remained invariable with chlorine. Write down it as follows: Zn0 - 2e-= Zn2+H + + e-= H0
4. From the decision it is clear that "to counterbalance" these two electrons given by zinc, quantity of the ions of hydrogen accepting electrons in the left member of equation it is necessary to double. Write down it the following equation: Zn + 2HCl = ZnCl2 + H2.
5. Checking amounts of atoms of elements in the left and right parts of reaction, make sure that the equation is solved correctly.
6. It is possible to solve the equation of oxidation-reduction reaction also by method of electronic and ion balance. Review the same example, only write down all initial substances and all products of reaction in an ionic form: Zn0 + H + + Cl-= Zn2 + + Cl-+ H20.
7. Having deleted identical ions in the left and right members of equation (chlorine ions), receive an abbreviated notation: Zn0 + H + = Zn2 + + H20.
8. It is easy to understand that for the equation of quantity of ions and charges, before a hydrogen ion in the left part it is necessary to deliver coefficient 2. And general view of the equation: Zn + 2HCl = ZnCl2 + H2.