"Ionic Reaction" PPT courseware

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"Ionic Reaction" PPT courseware

Part One: Learning Objectives

1. Understand the concept of electrolytes.

2. Know that acids, bases, and salts can ionize in solutions, and be able to write the ionization equations of acids, bases, and salts in solutions.

3. Understand ionic reactions and the conditions under which ionic reactions occur, be able to write ionic equations correctly, and judge whether ions coexist.

Ion reaction PPT, part 2: ionization of electrolyte

[Experiment 1-2] Phenomenon and conclusion: (1) Dry NaCl solid, dry KNO3 solid, and distilled water do not conduct electricity (2) NaCl solution and KNO3 solution can conduct electricity (3) Molten NaCl and KNO3 can conduct electricity.

Explanation: There are no freely moving ions in electrolyte solids and distilled water, so they cannot conduct electricity; there are freely moving ions in NaCl solution, KNO3 solution, molten NaCl, and molten KNO3, so they can conduct electricity.

1､Electrolytes and non-electrolytes

(1). Electrolyte: a compound that can conduct electricity in an aqueous solution or molten state. Such as NaCl, H2SO4, NaOH, etc.

(2). Non-electrolyte: a compound that does not conduct electricity in an aqueous solution or in a molten state. Such as alcohol, sucrose, etc.

2､Ionization

1). The reason why electrolytic solutions conduct electricity: Acids, alkalis, and salts can conduct electricity in aqueous solutions because they are ionized in the solution and produce ions that can move freely.

2).Ionization equation (expression method of electrolyte ionization):

(1) Ionization of acid: such as H2SO4:H2SO4=2H++SO2-4

(2) Ionization of base: such as KOH:__KOH=K++OH-

(3) Ionization of salt: such as Na2CO3:Na2CO3=2Na++CO2-3

3). Understand acids, bases and salts from the perspective of ionization

Inspired inquiry: Copper can conduct electricity at both room temperature and molten state. Is copper an electrolyte? Explain the reason.

Tip: No. Because copper is an element and electrolyte is a compound.

2､Ionization

(1) Concept: The process of dissociation of an electrolyte into freely moving ions when dissolved in water or in a molten state is called ionization.

(2) Scope of application of ionization: electrolytes. Acids, alkalis, and salts belong to electrolytes.

Acid: A compound in which all the cations produced during ionization are H+ are called acids.

Base: A compound in which all the anions produced during ionization are OH- are called bases.

Salt: When ionized, compounds that can produce metal cations (or NH+4) and acid anions are called salts.

(3) Conditions for ionization: When dissolved in water or melted by heat, acids, bases, and salts can ionize when dissolved in water or melted by heat. Alkali and salts can generally ionize when melted by heat.

Special reminder: ① The electrolyte solution conducts electricity and needs to be under the action of electric current, but the ionization of the electrolyte does not require the action of electric current. ② The electrolyte can only conduct electricity in an aqueous solution or molten state, such as solid NaCl, which does not conduct electricity. ③ The conductivity of the electrolyte is different from that in the solution since

It is related to the concentration of mobile ions. The greater the concentration of freely moving ions, the more charges the ions carry and the stronger the conductivity.

3. Ionization equation

The ionization of electrolytes is usually expressed in chemical terms-ionization equations.

For example: NaCl=Na++Cl- HCl=H++Cl- H2SO4=2H++SO2-4

Issues that should be noted:

(1) When writing the ionization equation, although each ion exists as a hydrated ion in the solution, for the convenience of writing, we still use simple ion symbols to represent hydrated ions.

(2) Writing the ionization equation must follow the two laws of mass conservation and charge conservation (in an electrolyte solution, the total number of positive charges carried by cations is equal to the total number of negative charges carried by anions).

(3) Acid does not ionize in the molten state, so do not write an ionization equation.

4. The concepts of acid, alkali and salt

(1) Acid: A compound in which all cations generated during ionization are hydrogen ions is called an acid, such as HCl=H++Cl-.

(2) Base: A compound in which all the anions generated during ionization are hydroxide ions is called a base, such as NaOH=Na++OH-.

(3) Salt: Compounds that generate metal ions or ammonium ions and acid ions during ionization are called salts, such as Na2SO4=2Na++SO42-.

Note: In middle school, water is neither an acid nor a base.

Ion reaction PPT, part three content: Ion reaction

1. Ionic reaction

The reaction of electrolytes in solution is essentially a reaction between ions. This reaction is called an ionic reaction.

2. Representation method of ionic reactions - ionic equation

(1) Concept: The formula that uses the symbols of the ions that actually participate in the reaction to express the reaction is called an ionic equation.

(2) Writing steps:

Take the reaction between Na2CO3 and hydrochloric acid as an example

①Write Correctly write the chemical equation of the reaction: Na2CO3+2HCl=2NaCl+H2O+CO2↑｡

②Decompose the substances that are easily soluble in water and easily ionized into ionic form, and the insoluble substances, gases and water are still expressed by chemical formulas. The above chemical equation can be rewritten as:

2Na++CO2-3+2H++2Cl-=2Na++2Cl-+H2O+CO2↑｡

③Delete Delete the ions that do not participate in the reaction on both sides of the equation.

CO2-3+2H+=H2O+CO2↑

④Check Check whether the number of atoms and the total number of charges of each element on both sides of the equation are equal.

(3) Meaning

①Indicates a specific chemical reaction

BaCl2+Na2SO4=BaSO4↓+2NaCl

The ionic equation is Ba2++SO2-4=BaSO4↓

②Indicates the same type of ion reaction

2. Conditions for metathesis reaction to occur

The metathesis reaction of acids, bases, and salts in aqueous solutions is essentially a reaction in which two electrolytes exchange ions with each other in the solution. The conditions for this type of ion reaction to occur are: generation of precipitation, release of gas, or generation of water. As long as the above conditions are met. 1, the reaction can occur.

Temptation to explore: Coarse salt contains Ca2+, Mg2+, SO2-4, etc. How to use ion reaction to remove the above ions? Write the relevant ionic equation.

Ion reaction PPT, part 4: knowledge point learning

Knowledge point 1 The concept of electrolyte

Example 1 The correct understanding of the concept of electrolytes is ( )

A. Substances with strong electrical conductivity

B. Any substance that can conduct electricity in aqueous solution

C. Substances that can conduct electricity in the molten state

D. Compounds that can conduct electricity in aqueous solution or molten state

[Analysis] A does not specify whether the substance is a compound or a simple substance. The statement is not strict and A is incorrect; B does not specify whether the ion is generated by the compound itself or a new substance generated by the reaction of the substance with water. For example, CO2 is not an electrolyte CO2+ H2O=H2CO3, carbonic acid solution can conduct electricity, H2CO3 is an electrolyte, therefore, B is incorrect; C does not specify the type of substance, for example, Cu can conduct electricity in the molten state, but Cu is not an electrolyte, C is incorrect; only D matches the electrolyte Concept, correct.

[Comments] This question mainly tests the correct understanding of electrolytes and the basis for judgment. To understand the concept of electrolytes, you must grasp several keywords: first, "compound", not a simple substance or a mixture; second, a condition in the molten state or aqueous solution Compounds that can conduct electricity; third, the "compound itself" ionizes to produce ions.

Knowledge Point 2: Ionization of electrolytes and conductivity of solutions

Example 2 Which of the following statements is correct ( )

A. The reason why sodium chloride crystals cannot conduct electricity is that there are no anions or cations in the sodium chloride crystals.

B. Under the action of electric current, magnesium chloride ionizes into magnesium ions and chloride ions in aqueous solution, expressed as MgCl2=Mg2++2Cl-

C. The reason why potassium chloride crystals cannot conduct electricity but its aqueous solution can conduct electricity is that potassium chloride reacts with water to produce potassium ions and chloride ions.

D. The reason why the crystal cannot conduct electricity is that the potassium ions and chloride ions that make up the potassium chloride crystal cannot move freely. After being dissolved in water, freely moving potassium ions and chloride ions are produced under the action of water molecules, so the aqueous solution can conduct electricity.

[Analysis] The ionization of electrolytes refers to the process of producing ions that can move freely when an electrolyte is dissolved in water or in a molten state. Ionization does not require an external current to occur, so item B is incorrect; sodium chloride crystals are composed of sodium ions and chlorine. It is composed of ions. The reason why the crystal is non-conductive is because the sodium ions and chlorine ions are bound to the crystal and cannot move freely, so item A is wrong; potassium chloride dissolves in water and no chemical reaction occurs. The potassium ions and chlorine ions in the aqueous solution Ionic potassium chloride crystals themselves contain.

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Update Time: 2024-11-19

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