"How to Write Chemical Equations Correctly" Chemical Equations PPT Courseware 2

Description

"How to Write Chemical Equations Correctly" Chemical Equations PPT Courseware 2

Knowledge review:

1. All chemical reactions must obey the law of _______?

Why is mass conserved?

In a chemical reaction, the types of atoms do not change before and after the reaction, the number does not increase or decrease, and the mass of the atoms does not change.

2. The chemical equation uses _______ to represent _______?

Qualitative meaning: Carbon and oxygen react under ignition conditions to form carbon dioxide.

The meaning of quantity: every 12 parts of carbon by mass reacts with 32 parts of oxygen by mass to produce 44 parts of carbon dioxide by mass.

The meaning of chemical equation:

1. Indicate reactants, products and reaction conditions

2. Represents the mass ratio between substances.

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

1. Principles of chemical equations

1. It must be based on objective facts, and must not be made up of imagination or fabrication of substances and chemical reactions that do not actually exist.

2. Comply with the law of conservation of mass. The types and numbers of atoms on both sides of the equal sign must be equal.

2. Steps for writing chemical equations

Take the reaction of phosphorus burning in the air to form phosphorus pentoxide as an example:

1. write

Write the chemical formula of the reactants on the left,

Write the biochemical formula on the right,

Connect both sides of the formula with a short line.

2. Matching: According to the law of conservation of mass, the appropriate stoichiometric number is added before the chemical formula on both sides of the formula to make the number of atoms of each element on both sides of the formula equal.

3. Standard

Indicate the conditions under which chemical reactions occur and the state of the products.

summary

1. Remember two principles when writing chemical equations:

(1) It is based on objective facts and cannot invent substances and chemical reactions that do not actually exist out of thin air.

(2) Obey the law of conservation of mass

2. When writing a chemical equation, appropriate stoichiometric numbers should be placed in front of the chemical formulas on the left and right sides of the formula to make the total number of atoms of each element equal. This process is the balancing of chemical equations.

3. The writing of chemical equations can be summarized as:

(Take the chemical equation writing of the reaction "potassium chlorate - potassium chloride + oxygen" as an example)

Give it a try:

1. Are the following chemical equations written correctly? If it is incorrect, explain why.

(1) Mercury oxide decomposes by heat

(2) Magnesium ribbon burns in oxygen

2. The drug cannabis (the chemical formula of the main component is C21H30O2) is burned in the air to generate carbon dioxide and water. The chemical equation of the reaction is:

3. The battery used in automobiles is a lead-acid battery. Its current intensity and power are far greater than ordinary dry batteries. Its working principle is: the PbO2 attached to the positive electrode reacts with the Pb attached to the negative electrode and the sulfuric acid in the electrolyte to generate PbSO4 and a common oxides. Please write the chemical equation for this reaction:

Among them, the valence of the lead element changes from ____ valence before the reaction to ____ valence after the reaction.

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Update Time: 2024-11-08

This template belongs to Chemistry courseware People's Education Press Ninth Grade Chemistry Volume 1 industry PPT template

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