"Chemical Equations" Source of Life - Water PPT Courseware

Description

"Chemical Equations" Source of Life - Water PPT Courseware

learning target

1. Understand the principles of writing chemical equations.

2. Master the steps of writing chemical equations.

3. Able to write and balance simple chemical equations correctly.

In conclusion

1. Principles of writing chemical equations

Based on objective facts, non-existent chemical reactions and chemical formulas cannot be invented out of thin air.

Complying with the law of conservation of mass, the type and number of atoms remain unchanged before and after the reaction.

2. How to write chemical equations

1. Write (write the chemical formulas of reactants and products)

2. Balance (balance to make the number of atoms before and after the reaction equal)

3. Wait (change the horizontal line into an equal sign)

4. Note (indicate the conditions of the reaction and the state of the product, that is, the chemical formula of the gas and water-insoluble solid in the product is generally marked with a "↑" or "↓" symbol)

5. Check (check whether the above parts are correct)

3. Balancing Methods of Chemical Equations

1. Balance basis: law of conservation of mass

2. Balance principle: Add appropriate stoichiometric numbers in front of the chemical formula (and make it into the simplest integer ratio), so that the types and numbers of atoms of each element in the reactants and products are equal (obey the law of conservation of mass), The small number in the lower right corner of the chemical formula indicating the number of atoms or atomic groups cannot be changed.

3. Precautions for trimming:

(1) Match ________ first, then ________.

(2) Select the atoms that appear _________ times at both ends to balance them first.

4. Balance method:

(1) Least common multiple

(2) Fraction method

Practice in class

2H2 + O2 ignites H2O

3Fe + O2 ignites Fe3O4

Fe3O4 + H2 High temperature Fe + H2O

2 CuO + C High temperature Cu + CO2

In conclusion

1. Chemical equations must be written based on the facts of chemical reactions, and chemical equations for reactions that do not actually exist must not be subjectively invented.

2. Be sure to balance the chemical equation. When balancing, only the coefficient is allowed in front of the chemical formula, and the chemical formula cannot be changed.

Knowledge point 1. Determine whether chemical equations are correct or incorrect

[Typical Example 1] Which of the following chemical equations is correct ( )

A.2Mg+O2====2MgO

B.2KMnO4 ==== K2MnO4+MnO2+O2↑

C.HgO====Hg＋O2↑

D.H2O2====H2↑+O2↑

① Whether the chemical equation is balanced;

② Whether the precipitation symbols and gas symbols are marked and whether they are marked correctly;

③Whether the chemical reaction conforms to objective facts;

④Whether the reaction conditions are labeled and whether the labeling is correct.

Knowledge point 2: Writing chemical equations

[Typical Example 2] (2010 Nan'an High School Entrance Examination) During construction, a mixture of aluminum and iron oxide (Fe2O3) is often ignited, and a large amount of heat is released during the reaction to weld the gaps in the rails, and generate alumina and molten of iron. The chemical equation of the reaction is 2Al + Fe2O3====2Fe+ Al2O3.

Knowledge point three: Determine the chemical formula and measurement number of substances in chemical equations

1. In the reaction equation 4Cu + 10HNO3 = 4Cu(NO3)3 + X + 5H2O, the chemical formula of X is:

A NO B NO2 C N2O D N2O3

2. Titanium dioxide (TiO2) is a widely used chemical raw material. Titanium dioxide can be produced by reacting titanium tetrachloride (TiCl4) with a common substance X. The chemical equation of the reaction is TiCl4+□X = TiO2+4HCl. Regarding substance X, which of the following statements is correct ( )

A. This substance is composed of three elements: carbon, hydrogen, and oxygen.

B. The chemical formula of this substance is H2O2

C. The mass ratio of hydrogen and oxygen elements in this substance is 1:8

D. The mass fraction of hydrogen element in this substance is 5%

knowledge training

1. Among the following principles or steps for writing chemical equations, which one is incorrect ( )

A. Must follow the law of conservation of mass

B． Be sure to indicate the reaction conditions

C. Indicate the state of the product (gas, precipitation)

D． In the process of balancing chemical equations, it is necessary to change the corner codes of the element symbols in the chemical formula, so that the balancing is easier.

2. The information that cannot be expressed by chemical equations is ( )

A. Speed ​​of chemical reaction B. Reactants and products

C. Conditions of reaction D. Mass relationship between substances

3. In the chemical reaction: 2X2 + 3Y2 ====2R, use X and Y to represent the chemical formula of R. The correct one is ( )

A. X2Y2 B. X2Y3 C. X4Y5 D. X3Y2

Writing chemical equations can be summarized as

A horizontal line appears on the left and right side

Add a line after trimming

Conditions for betting on equal signs

Arrow marks gas or sediment

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Update Time: 2024-11-24

This template belongs to Chemistry courseware Cantonese Education Edition Ninth Grade Chemistry Volume 1 industry PPT template

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