A chemical equation is a formula that uses a chemical formula to express a chemical reaction, which not only expresses the relationship between reactants and products, but can also be used to calculate the quantitative relationship between reactants and products. 1. Set the unknowns, the physical quantities of the matter, the unified symbols, etc.
2.Writing a chemical equation first requires writing the equation for the chemical reaction, which includes the molecular formulas and coefficients of the reactants and products. 3.Determining the Relationship of the Quantities of Each SubstanceAccording to the chemical equation, the relationship between the quantities of reactants and products can be determined. In particular, the quantitative relationship between a known substance and an unknown substance. 4.Column proportions are proportional to relation quantities and known quantities and unknown quantities. 5. Seek the result and. Perform Experimental VerificationAfter the calculations are performed, experimental verification is required to confirm the accuracy of the calculation results. During the experiment, it is necessary to operate in strict accordance with the proportion of chemical equations, and pay attention to the observation of experimental phenomena and record data. If there is a deviation between the experimental results and the calculated results, the calculation process needs to be checked to find the error**.
Key points in the calculation of the amount of a substance.
1) Writing standard: The writing of various symbols should be standardized, and the meaning of uppercase letters and lowercase letters is different. For example, "m" denotes molar mass, while "m" denotes mass, "n" denotes the number of particles, and "n" denotes the amount of matter.
2) Symbol Specification:
Let the unknowns be directly represented by the symbols of each physical quantity, and the symbol of the substance (or particle) should be indicated. If the volume of HCl solution participating in the reaction is V[HCl(AQ)].
The names and formulas of physical quantities and units, substances, etc., should be represented by symbols as much as possible. If the volume of the NaOH solution and the concentration of the substance are known, the mass of the NaOH solution is written as: M(NaOH) C(NaOH) V[NaOH(AQ)] M(NaOH).
3) Unit specification: substitute the known quantity into the calculation formula, and the unit should be unified when calculating.
4) The ratio of the stoichiometric numbers of each substance in the chemical equation is equal to the ratio of the amount of the substances of each substance.
5) When calculating according to the chemical equation, the principle of physical quantity selection is: the top and bottom are consistent, and the left and right are equal.