Stoichiometric number: in the chemical reaction equationcoefficient, stoichiometric number, denoted by ν.In fact, in application, it is the balance of the equation. If the equation is usedUndetermined coefficient methodAfter balancing, the figure obtained is its coefficient, that is, the measured number.
Chinese name
Stoichiometric number
Foreign name
stoichiometric number
Pronunciation
huà xué jì liàng shù
Substantive interpretation
Number obtained from the balance of equation
Not capable
No connection between micro and macro
Role
Reveal the relationship between chemical reaction components
Richter clearly put forward for the first time in his book Preliminary Chemometrics (1792-1794) that "elements have a fixed mass ratio to each other", which is the first time that the theory of multiple laws has been clearly expounded.This is the early prototype of "stoichiometric number".Later, Dalton put forward a new atomism in the New System of Chemical Philosophy published in 1808.At this point in history, people have been able to determine the proportion of each element in most known chemical species, and "measurement number" has also begun to be widely used.[1]
definition
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Stoichiometric number: In the chemical reaction equation, the coefficient in front of the substance participating in the reaction is called the stoichiometric number, which is denoted by ν.In fact, in application, it is the balance of the equation. If the equation is usedUndetermined coefficient methodAfter balancing, the figure obtained is its coefficient, that is, the measured number.The concept of stoichiometric number should include its connotation and extension, that is, the ratio of stoichiometric number toNumber of particlesRatioAmount of substanceRatio, gas volume ratioreaction rateThe relation of ratio and equality.[2]
Specific description
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The stoichiometric point is the theoretical value obtained according to the chemical reaction relationship.
aboutChemical equationIn front of the chemical formula of each substance in“coefficient”(i.e., stoichiometric number) should not be simply regarded as the number of atoms or molecules. In fact, the reaction phenomena that we can observe are by no means the result of several atomic and molecular reactions, but the macroscopic phenomenon shown by the aggregation of a large number of particles.The chemical equation also has the following formula:Amount of substanceRatio "[2]
Writing method
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To followLaw of conservation of massandchemical reactionObjective facts.The law of conservation of mass refers to participationchemical reactionThe sum of the mass of each substance is equal to the sum of the mass of each substance generated after the reaction.The stoichiometric number is inseparable from the writing of chemical equation, which will be discussed here.
Principles of Writing Chemical Equations
① The chemical formula of reactants is written on the left, and the chemical formula of products is written on the right, with "=" connected in the middle.
②Chemical equationThe balancing of is to add necessary coefficients in front of the chemical formula of reactants and products so that the number of atoms of each element in the reactants and products is equal.
③ The conditions required for the reaction shall be noted. If heating is required, the use of catalyst, etc. shall be carried out inEqual signWrite above.If two or more conditions are required, the heating conditions are generally written below the equal sign (or represented by Δ)
④ Indicate the product status, and use "↑" to indicate YesGas generation(There is no gas in the reactant), "↓" means that there is insoluble matter (precipitation) or solid formation (there is no solid or precipitation in the reactant).[3]
Steps for writing chemical equations
1. Write: Write the chemical formula of reactants and products according to the facts (left opposite, right opposite), and draw a short line between the reactants and products.
2. Matching: The purpose of balancing the chemical equation is to make the type and number of atoms on both sides of the equal sign equal, abide by the law of conservation of mass, and check after balancing.
3. Note: indicate the conditions under which the chemical reaction occurs (ignition, heating, etc.), mark the product state (gas, precipitation, etc.), and change the short line to an equal sign.
4. Check: check whether the chemical equation is correct.[3]
Balance of chemical equation
①Least common multipleMethod: A. Find out the atoms with a large number of atoms and a single pair on both sides of the reaction formula, and find its least common multiple.
② Odd even number method: there is an odd and even number of atoms on both sides of the reaction formulaOdd numberChange even number, and then trim.[3-4]
Application and transformation
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Stoichiometric action
withintegerTo revealchemical reactionThe relationship between components can be measured not only byatomThe ratio between the number of reactions can also be extended to macroAmount of substanceMass can also be a relationship between volumes.Moreover, the measurement number can be outstandingValenceThe quantitative relationship of electron transfer.
Stoichiometric number and reaction order
Reaction order: in the rate equation of chemical reaction, the reaction order of the reaction is the sum of the exponent of the concentration term of each reactant.
The relationship between the reaction order and the stoichiometric number: the grading number of the elementary reaction reactant is equal to the absolute value of the stoichiometric number of the reactant;For non elementary reactions, they are not necessarily equal.
