# Advice 1: How to solve the chain in chemistry

In order to successfully solve the chain of chemical transformations of one substance into another, it is necessary to study the properties of substances, their interactions and characteristics of each class of compounds. Among the qualitative objectives, the decision-chain substances are the most common.
Instruction
1
Carefully read the problem statement. If needed, you can do it more than once.

Write the equation by which you can obtain the following transformation: Al → Al(NO3)3 → Al2O3 → Al(OH)3 → K[AL(OH)4] → AlCl3 → Al(NO3)3 → AlPO4. For each transformation make reaction equations. If the transition of one stage is impossible, make two or more reaction equations.
2
Write down the chain separately, the conditions of the problem. You can number the number of reactions and whether the substance for convenience. Remember that every substance is the source for later. Determine to what class of substances to treat each member of the chain. The first number is the metal aluminium. the initial reaction product should be salt. The properties of the metal salt is obtained by interaction with the acid. In this case, with nitric acid. Consider whether this reaction. Make a diagram of the equation arrange the coefficients. The first conversion is ready. Follow step by step, gradually moving to the last substance, the phosphate of aluminium.
3
Check yourself again. Nurse look at equations reactions, check everywhere there are the desired coefficients. Don't forget to properly execute the reactions. Have redox compose the electronic balance, make quick schemes for ionic reactions.
The decision
1.Al + 6HNO3(conc.) => Al(NO3)3 + 3NO2 + 3H2O

2.4 Al(NO3)3 => 2AL2O3 + 12NO2 + 3O2

3.Al2O3 + 3H2SO4 => Al2(SO4)3 + 3H2O

Al2(SO4)3 + 6NaOH => 2Al(OH)3 + 3Na2SO4

4.Al(OH)3 +KOH => K[Al(OH)4]

5.K[Al(OH)4] + 4HCl => KCl + AlCl3 + 4H2O

6.AlCl3 + 3AgNO3 => Al(NO3)3 + 3AgCl

7.Al(NO3)3 + K3PO4 => AlPO4 + 3KNO3

# Advice 2: How to solve equations of chemical reactions

Chemical reactions called the transformation of certain substances having a specific composition and properties, other substances with a different structure and other properties. In this transformation, no changes in the composition of atomic nuclei does not occur. This is the main difference of the chemical reactions from those that occur in a nuclear reactor.
Instruction
1
Consider a typical chemical reaction, which is familiar to almost any person. What happens when you make a fire? Organic fuel (in this case, wood), or rather its main component, the carbon enters the oxidation reaction with oxygen in the air. A chemical reaction takes place, accompanied by less abundant evolution of heat, there is a flame. It is written thus:
C + O2 = CO2 Or, for example, the conversion of calcium oxide (quicklime) to calcium hydroxide (slaked lime):
CaO + H2O = Ca(OH)2
2
You should remember that, unlike mathematical equations, the equations of chemical reactions left and right parts must not be interchanged! Substances in the left part of equation of a chemical reactionare called reactants, and those on the right side – reaction products.
3
It is also necessary to correctly write the formulas of the starting materials and products. Then make sure that this chemical reaction possible, that is, its occurrence does not contradict known physical and chemical laws and regulations. For example, the reaction AgNO3 + NaCl = NaNO3 + AgCl is possible, and the reverse reaction:
AgCl + NaNO3 = NaCl + AgNO3 - no, because silver chloride is almost insoluble. And, despite the fact that the formulas of the substances are written correctly, this reaction is not feasible.
4
We need to ensure that the number of atoms of each element participating in the reaction, left and right side is the same. This is the main indicator of the correctness of the decision of the equation of the chemical reaction. Example: how to solve an equation of this chemical reaction as the hydrogen reduction of iron from iron oxide of trivalent? Write the starting materials and reaction products.
Fe2O3 + H2 = Fe + H2O
5
You will immediately see that the coefficient before the formula of water on the right side of the reaction must be a multiple of 3 (since the left side already has three atoms of oxygen). Check this ratio. You will get:
Fe2O3 + H2 = Fe + 3H2O
6
By elementary selection, you'll find that in the left and right side of the equation should be: 2 atoms of iron, 3 atoms of oxygen, 6 hydrogen atoms, 3 oxygen atoms. So, the final entry of the equation of chemical reaction is this:
Fe2O3 + 3H2 = 2Fe + 3H2O
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