"How to Write Chemical Equations Correctly" Chemical Equations PPT Courseware 5

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"How to Write Chemical Equations Correctly" Chemical Equations PPT Courseware 5

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The cinder left after coal is burned has obviously become lighter. Can you express it using a chemical equation?

What is its significance?

On what basis did you write this equation?

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.

1. There are two principles to follow when writing chemical equations:

Must be based on objective facts

Must obey the law of conservation of mass

Balancing chemical equations:

According to the law of conservation of mass, the chemical formula on both sides of the formula is preceded by the appropriate stoichiometric number to make the number of atoms of each element on both sides of the formula equal.

How to balance chemical equations

1. Observation method: Determine stoichiometric numbers entirely by observation to balance chemical equations. It is suitable for balancing simple chemical equations.

2. Least common multiple method: Select the atom that appears only once on the left and right and has the largest number as the starting point, find its least common multiple, and then divide the least common multiple by the number of the atom in different chemical formulas as the stoichiometric number of the chemical formula, and Other stoichiometry numbers can be deduced from this.

3. Odd pairing method: When atoms of a certain element appear the most often, and one is odd and one is even on the left and right sides, a 2 is often placed in front of the chemical formula corresponding to the odd number of atoms, and other stoichiometric numbers can be derived from this.

2. Writing steps

Write Write the chemical formulas of the reactants and products and connect them with dashes or arrows.

Balancing chemical equations, least common multiple method

Note: Indicate the reaction conditions and the state of the product.

etc. Change the dash or arrow to an equal sign

summary:

1. Definition: Use chemical formulas to express chemical reactions.

2. Meaning:

(1) Indicate reactants, products and reaction conditions

(2) Represents the mass ratio between each substance,

(3) Represents the particle number ratio between each substance,

3. Writing principles

First, it must be based on objective facts

Second, we must abide by the law of conservation of mass. The types and numbers of atoms on both sides of the equal sign must be equal.

4. Writing steps:

Write: reverse left and create a horizontal line on the right

Equip: balance

Note: Indicate reaction conditions and product status.

Etc.: Change the short line to the equal sign

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Update Time: 2024-09-30

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

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