"Chemical Equations" Source of Life - Water PPT Courseware 2

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"Chemical Equations" Source of Life - Water PPT Courseware 2

think

1. What is the law of conservation of mass?

Why is mass conserved?

2. Please observe the difference between the following expressions?

P + O2→P2O5

4P + 5O2→2P2O5

3. What is a chemical equation?

What is the significance of chemical equations?

1. Chemical equation

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

2. Meaning:

①Indicates reactants, products and reaction conditions

②Indicates the mass relationship between various substances (i.e. the ratio of the product of relative molecular mass and coefficient)

③Indicates the ratio of the number of atoms and molecules between each reactant and product

What does a chemical equation mean?

1. Qualitative aspect:

Carbon and oxygen react under ignition conditions to form carbon dioxide

2. Quantity aspect:

Every 12 parts of carbon and 32 parts of oxygen react completely to produce 44 parts of carbon dioxide.

3.Micro aspects:

1 carbon atom reacts with 1 oxygen molecule to produce 1 carbon dioxide molecule

Try to tell the meaning of the following chemical equation

1. Qualitative aspect: Phosphorus and oxygen generate phosphorus pentoxide under ignition conditions

2. In terms of quantity: every 124 parts by mass of phosphorus reacts completely with 160 parts by mass of oxygen to produce 284 parts by mass of phosphorus pentoxide.

3. Microscopic aspect: 4 phosphorus atoms and 5 oxygen molecules react to generate 2 phosphorus pentoxide molecules

summary

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)

Invert the left and create a horizontal line on the right: KClO3——KCl + O2

After trimming, add a line 2KClO3==2KCl + 3O2

The arrow marks gas or precipitation 2KClO3==2KCl + 3O2

Class exercise one:

1. Iron + oxygen → ferric oxide

3Fe + 2O2==Fe3O4

2. Methane + oxygen → water + carbon dioxide

CH4 + 2O2==CO2 + 2H2O

3. Potassium permanganate (KMnO4) → Potassium manganate (K2MnO4) + manganese dioxide + oxygen

2KMnO4==K2MnO4 + MnO2 + O2

Class Exercise 2

Judge whether the following reaction equation is correct based on the knowledge you have learned. If there are any errors, please point them out.

(1) 3Fe + 2O2==Fe3O4

(2)Mg + O2==MgO2

(3)HgO==Hg + O2

Notes on calculations based on chemical equations:

(1) Calculate the product of the relative molecular mass (or relative atomic mass) of each chemical formula and the measurement number in front of the chemical formula based on the composition of the substance and the chemical equation. The calculation must be accurate.

(2) The writing format of problem solving should be standardized.

(3) Pay attention to the writing requirements of the unit.

Notes on calculations based on chemical equations:

(1) All quantities substituted into chemical equations for calculation must be the mass of pure substances. If they are impure substances, they need to be converted.

Mass of pure substance = Mass of impure substance × Purity = Mass of impure substance × (1 – Mass fraction of impurities)

(2) The volume of gas and liquid must be converted into the mass of gas and liquid.

Gas mass (g) = gas volume (L) × density (g/L)

Liquid mass (g) = liquid volume (mL) × density (g/mL)

(3) If only the mass of one substance is given in the question, the amount of the other substance is often described as "sufficient", "appropriate amount", "excess" or "complete reaction", "exactly complete reaction", etc. . If the masses of both reactants are known at the same time, the excess problem needs to be considered.

(4) Pay attention to the unit of the known mass; when setting the unknown, the mass of ××× should be set to On the unit. (If no explanation is given, keep it to one decimal place)

practise

1. When the following substances of equal mass are completely burned in oxygen, the one that consumes the most oxygen is ( )

A． Hydrogen gas b. Red phosphorus c. Sulfur D. iron

Idea: Write the reaction equation, make appropriate deformations, and make the measurement numbers before the chemical formula of oxygen equal (both are 1), and then observe and compare. Generally, there is no need to calculate the final result.

2. Equal masses of iron and zinc react with a sufficient amount of dilute hydrochloric acid respectively. The known chemical equations of the reactions are: Fe+2HCl=FeCl2+H2↑, Zn+2HCl=ZnCl2+H2↑. Then the mass of hydrogen produced is ( )

A． equal b. Iron is greater than zinc C. Iron is smaller than zinc D. Can't compare

Idea: Fe+2HCl = FeCl2+H2↑ Zn+2HCl = ZnCl2+H2↑

3. There are two elements, X and Y. 12gX2 reacts with XY3 to produce 24gC. If the chemical equation of the reaction is X2 +

A.1�1 B.1�2 C.3�1 D.3�4

4. Fully heat the powdered mixture containing 15 grams of A, 10 grams of B, and 9 grams of C to cause a chemical reaction. 3 grams of A remain, B increases to 25 grams, C has been consumed, and gas D is released. The reaction process The value of the ratio A�B�C�D of the mass change of the substance in is ( )

A. 5�4�3�2 B. 4�5�3�2

C. 3�2�4�5 D. 2�3�5�4

5. There are 15 grams of each of three substances A, B, and C. Under certain conditions, only 30 grams of D will be produced when the reaction is complete. If 10 grams of C are added, A and C will react completely. Then the mass ratio of A and B participating in the reaction is ( )

A. 3：2 B.2：3 C.5：22 D.5：3

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Update Time: 2024-08-02

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

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