"Chemical Equations" Quantitative Study of Chemical Reactions PPT Courseware

Description

"Chemical Equations" Quantitative Study of Chemical Reactions PPT Courseware

learning target

1. Understand the meaning and pronunciation of chemical equations;

2. Understand the principles that should be followed when writing chemical equations;

3. Be able to write simple chemical equations correctly.

Knowledge points

1. The meaning of chemical equations

This kind of chemical formula that expresses a chemical reaction is called a chemical equation.

Information provided by chemical equations:

1. Indicate the reactants

2. Indicate reaction conditions

3. Represents the ratio of the number of particles between various substances

4. Indicate the product

The meaning of chemical equation:

(1) Representing reactants, products and reaction conditions (macroscopic meaning)

Example: Indicates that carbon and oxygen react under ignition conditions to produce carbon dioxide

(2) Indicates the mass ratio of each substance between reactants and products (macroscopic meaning)

Example: It means that every 12 parts of carbon by mass reacts completely with 32 parts by mass of oxygen to produce 44 parts by mass of carbon dioxide.

(3) Represents the ratio of the number of particles in reactants and products (microscopic meaning)

(The particle number ratio is the ratio of the stoichiometric numbers in front of the chemical formula)

Example: Each carbon atom reacts with one oxygen molecule to produce one carbon dioxide molecule.

2. Principles to be followed when writing chemical equations

1. It must be based on objective facts and must not be based on imagination.

2. The law of conservation of mass must be followed, and the type and number of atoms before and after the reaction must be equal.

3. Writing chemical equations

One write

Second match

three standards

Balancing chemical equations

1. Things to note

① Chemical equations cannot have the same chemical formula on both sides of the equal sign.

② When balancing, you can only put a certain stoichiometric number in front of the chemical formula, but you cannot change the number in the lower right corner of the chemical formula.

③ The stoichiometric number 1 can be omitted. The stoichiometric number before each chemical formula must be the simplest integer ratio.

2. Method of balancing equations

(1) Least common multiple method

Key points: Find the elements that appear once on both sides of the chemical formula, balance the elements with unequal and large numbers of atoms, and find their least common multiple.

(2) Observation method

① The atomic group remains unchanged before and after the reaction. Consider the balance as a whole.

② If a certain atom appears multiple times before and after the reaction, the reaction characteristics can be observed first and then balanced.

Observing the above formula, the analysis shows that the CO before the reaction becomes CO2 after the reaction, that is, each CO can get 1 O atom, and there are 3 O oxygen atoms in Fe2O3, so 3 should be added before CO, and the others should be balanced accordingly.

(3) Odd-numbered spouse law

Choose the element that appears most frequently in the chemical formula and has an odd and even number of atoms.

The number of O's on the left side of the equation is 3, and the number of O's on the right side of the equation is 2. First match the number of O's on the left to an even number, that is, match 2 in front of KClO3, and then balance accordingly.

Methods and techniques

Balancing chemical equations is the focus of this lesson. On the basis of correctly understanding the content in the textbook, you can expand on some other balancing methods, and on the basis of frequent practice, summarize and summarize to find the easiest way to balance chemical equations. Methods and rules to improve your problem-solving efficiency.

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Update Time: 2024-10-03

This template belongs to Chemistry courseware Beijing Curriculum Reform Edition Ninth Grade Chemistry Volume 1 industry PPT template

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