Chemistry (converting literal expressions into chemical equations) 1.h2+02-h20 2.h2+o2-hcl 3.c+o2- 4.s+o2- 5.hg+o- 6.p+o2- 7.fe+o2- 8.mg+o2-mgo

Chemistry (converting literal expressions into chemical equations) 1.h2+02-h20 2.h2+o2-hcl 3.c+o2- 4.s+o2- 5.hg+o- 6.p+o2- 7.fe+o2- 8.mg+o2-mgo

（1）2H2+O2=2H2O
（2）H2+Cl2=2HCl
(3) C + O2 = CO2 or 2C + O2 = 2CO
(4)S+O2=SO2
(5)2Hg+O2=2HgO
(6) 4P + 3O2 = 2p2o2 or 4P + 5o2 = 2p2o5
(7) 4Fe + 3O2 = 2fe2o3 or 3Fe + 2O2 = 2fe3o4
（8）2Mg+O2=2MgO
The method is to balance. The specific method of balancing is to balance
1、 Least common multiple method
The specific steps are as follows: (1) find out the least common multiple of each atom before and after the reaction; (2) make the atom be the least common multiple before and after the reaction; (3) generally start with the oxygen atom, and then balance other atoms
Example: balance Al + Fe3O4 → Fe + Al2O3
The first step is to balance the oxygen atoms Al + 3fe3o4 → Fe + 4al2o3
The second step: balance iron and aluminum atoms 8Al + 3fe3o4 → 9fe + 4al2o3
Step 3: balance the chemical equation:
8Al + 3Fe3O4 9Fe + 4Al2O3
2、 Observation method
The specific steps are as follows: (1) to deduce the stoichiometric number of the chemical formula of the reactant and the stoichiometric number of the product from a product with complex chemical formula; (2) to find out the pour out stoichiometric number of other chemical formulas according to the stoichiometric number of the obtained chemical formula, so as to balance
For example: Fe2O3 + CO -- Fe + CO2
Observation:
Therefore, one Fe2O3 should give three "O" to three CO to transform them into three CO2
Fe2O3 + 3CO——Fe + 3CO2
If you look at the above equation again, there are two Fe (Fe2O3) on the left, so the coefficient of Fe on the right should be 2
Fe2O3 + 3CO 2Fe + 3CO2
In this way, we can get the chemical equation of the balance, and pay attention to change the "--" line into the "= =" sign
Fe2O3 + 3CO == 2Fe + 3CO2
Example: balance H2O + Fe → Fe3O4 + H2
The first step is to balance the oxygen atom 4H2O + Fe → Fe3O4 + H2
The second step: balance the hydrogen and iron atoms 4H2O + 3Fe → Fe3O4 + 4h2
Step 3: chemical equation after balancing:
4H2O + Fe Fe3O4 + 4H2
3、 Odd double method (odd variable even method)
The specific steps are as follows: (1) to find out the element that appears most frequently in the chemical reaction; (2) to start with the element with odd atomic number (usually oxygen element), that is, to multiply by 2; (3) to determine the stoichiometric number of other chemical formulas from the derived stoichiometric number
Example: balance FeS2 + O2 → Fe2O3 + SO2
The first step: multiply 2 FeS2 + O2 → 2fe2o3 + SO2 before Fe2O3
The second step: balance 4fes2 + O2 → 2fe2o3 + SO2
The third step: balance sulfur atom 4fes2 + O2 → 2fe2o3 + 8so2
Step 4: balance the oxygen atom
4FeS2 + 11O2 2Fe2O3 + 8SO2
4、 Fractional balance method
This method can balance the chemical reactions in which the elementary substance participates in the reaction or forms
The specific steps are as follows: (1) first balance the atoms of each element in the compound; (2) balance the atoms of elemental elements with fractions; (3) remove the denominator to make the balanced stoichiometric number an integer
Example: balance C2H2 + O2 → CO2 + H2O
The first step is to balance the carbon and hydrogen atoms in the compound C2H2 + O2 → 2co2 + H2O
The second is to balance C2H2 + 5 / 2O2 → 2co2 + H2O with fraction
Step 3: remove the denominator, that is, multiply all by 2 to get the balanced chemical equation
2C2H2 + 5O2 4CO2 + 2H2O
The above methods are not isolated, but can be applied in connection with each other. No matter which method is used, the characteristics of the reaction equation should be observed first, and then the appropriate balancing method should be determined. Generally speaking, the order of observation and balancing is as follows: hydrogen with hydrogen, oxygen without hydrogen. The priority of atomic group balancing, and the final balancing of single substance