Phản ứng trao đổi ion: Điều kiện xảy ra phản ứng và viết phương trình ion rút gọn

The ion exchange reaction in the electrolyte solution is one of the basic and important knowledge in the 11th grade chemistry program. So what is the ion exchange reaction, what is the condition that the reaction occurs and writing the shortened ion equation? Join Money to find out this content in the article below.

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What is the ion exchange reaction in the solution of electrolytes?

The ion exchange reaction is a reaction that occurs when substances participate in the ion exchange reaction. More specifically, this is a reversible chemical reaction, in which an ion has a lost atom or molecule or receives an electron, thus receiving a charge from a water solution exchanged for a similar charge ion attached to a positive charge.

Classification of ion exchange reactions

The type of ion exchange reaction (if any) is as follows:

• Salt + Acid → New salt + New acid

• Salt + base → New salt + new bases

• Salt + salt → New salt + new salt

• Hidroxit (insoluble) + Acid solution → Salt solution + H2O (weak electrolyte)

• Acid solution + Bazo solution → Salt solution + H2O (weak electrolyte)

3 conditions of ion exchange reactions in electrolytes

What is the condition of ion exchange reaction in electrolytes? According to the law of Bertholet, the ion exchange reaction occurs when the ions combine and form at least one of the following substances:

• Precipitate

• Weak electrolyte

• Gas

The reaction forms precipitate

To find out the condition of ion exchange in the solution of electrolytes, the following experiment is done: small Na2SO4 into the BaCl2 test tube. Observing the phenomenon of white precipitation of BASO4.

Reaction equation: Na2SO4 + BaCl2 → BaSO4 (precipitate) + 2naCl

The cause of this phenomenon is both Na2SO4 and BaCl2 are easily dissolved and dissociated in water:

Na2SO4 → 2NA + + SO4 (2-)

BaCl2 → Ba (2+) + 2Cl-

Among the dissociation ions, only three (2+) and SO4 (2-) are combined and produce baSO4 precipitate, so the nature of the ion exchange reaction will be:

Ba (2+) + SO4 (2-) → baSO4 (precipitate).

This is also known as the shortened ion equation. This equation shows the nature of the reactions in the solution of electrolytes.

How to write a shortened ion equation as follows:

• Converting soluble substances, strong electrolytes into ions

• Weak gas, precipitate and electrolytes remain in the form of molecules.

For example:

Full ion equation:

2NA + + SO4 (2-) + Ba (2+) + 2Cl- → baSO4 (precipitate) + 2NA + + 2Cl-

Shortened equation:

Ba (2+) + SO4 (2-) → baSO4 (precipitate)

From this equation, we can conclude, want to prepare the precipitate baSO4, need to mix two solutions: solution containing Ba (2+) and solution containing SO4 (2-).

The reaction forms a weak electrolyte

One of the conditions that the ion exchange reaction occurs in electrolytes is the reaction that forms a weak electrolyte, including: the reaction forms water and the reaction to form a weak acid.

Reaction to form water

The experiment is conducted, dripping a few drops of phenolphtalein solution into the cup of 0.10M NaOH solution. At this time the solution is pink. Then, slowly pour the 0.10M HCl solution into the cup, pouring and stirring according to the equation: HCl + NaOH → NaCl + H2O. Observe the phenomenon of discoloration solution.

The cause of this phenomenon is that NaOH and HCl are easily dissolved, strongly dissociated in water.

NaOH → Na + + OH-

HCl → H + + Cl-

OH- ions in solutions make pink phenolphtalein. H+ ions react with OH- ions to form H2O – a very weak electrolyte.

Redened equation: H + + OH- → H2O

The reaction forms weak acids

In this case, the experiment is given as follows: Small HCl solution into the test tube containing CH3COONa, weak acid CH3COOH will form:

HCl + CH3COONa → CH3COOH + NaCl

Explaining this, both HCl and CH3COONa are soluble and strong dissolved substances.

HCl → H + + Cl-

CH3COONa → Na+ CH3COO-

H+ ions combine with CH3COO ions – form CH3COOH – a weak electrolyte.

Redened equation: H + + CH3COO- → CH3COOH

The reaction forms gas

The reaction to form gas is one of the basic conditions for ion exchange reaction in electrolytes created.

To prove this, we conduct the experiment: Pour the HCl solution into the Na2CO3 container. The observed phenomenon is that air bubbles escape with the equation:

2HCl + Na2CO3 → 2naCl + CO2 ↑ + H2O

The cause of this phenomenon is that HCl and Na2CO3 are easily soluble and strongly dissociated in water:

HCl → H + + Cl-

Na2CO3 → 2NA + + CO3 (2-)

H+ and CO3 (2-) ions combine to form H2CO3 – an unstable weak acid, decomposing into CO2 and H2O.

H + + 2CO3 (2-) → HCO3-

H + + HCO3- → H2CO3

H2CO3 → CO2 ↑+ H2O

We have a shortened ion equation:

2H + + CO3 (2-) → CO2 (↑) + H2O

The reaction between acid solution and carbonate salt is very likely to occur because both forming weak electrolytes (H2O), and produces CO2 from the reaction.

For example, carbonate salts are less soluble in water but easily soluble in acid solutions.

For example, CaCO3 limestone is very soluble in HCl:

CaCO3 (R) + 2H + → Ca (2+) + CO2 (↑) + H2O

See also: What is electrolyte? Theory and detailed exercises

Exercise on ion exchange reaction of chemical textbook 11 with detailed solutions

To master the knowledge of the ion exchange reaction in the solution of electrolytes, we refer to some basic types of exercises in the 11th chemistry textbook with a brief and detailed solution below.

Lesson 1 page 20 textbook chemistry 11

What is the condition for the ion exchange reaction in the electrolyte solution? Take illustrative examples?

Solution:

According to the Bertholet’s law, this reaction only occurs when the ions combine and form at least one of the substances: precipitate, weak electrolytes and gases.

For example:

After the reaction forms a precipitate

Na2CO3 + CaCl2 → 2naCl + CaCO3 ↓

2NA + + CO3- + Ca2 + + 2Cl- → 2NA + + 2Cl- + CaCO3 ↓

Ca2 + + CO3- → CaCO3 ↓

After the reaction forms a volatile substance

Na2S + 2HCl → 2naCl + H2S ↑

2NA + + S2- + 2H + + 2Cl- → 2NA + + 2Cl- + H2S ↑

2H + + S2- → H2S ↑

After the reaction forms a weak electrolyte

2CH3COONa + H2SO4 → 2CH3COOH + Na2SO4

2CH3COO- + 2NA + + 2H + + SO42- → 2CH3COOH + 2NA + + SO42-

CH3COO- + H + → CH3COOH

Lesson 2 textbook chemistry 11 page 20

Why are the reactions between acid and hydroxide solutions that are basic and reaction with carbonate salts and acid solutions that are likely to occur?

Solution:

The product of the reaction between acid and hydroxide solution is salt and water (H2O), which is weak electrolyte.

Example: Mg (OH) 2 + 2HCl → MgCl2 + 2H2O

The product of the reaction between carbonate salts and acidic solution is new, and carbon dioxide (H2CO3) is very weak, easily decomposed into water (H2O and carbon dioxide (CO2) so the final product after the reaction has volatile substances (CO2) and weak electrolytes (H2O).

For example: CaCO3 + 2HCl → CaCl2 + CO2 ↑ + H2O

According to the condition of the exchange reaction, the above reaction may occur.

Lesson 3 textbook page 20 Chemistry 11

Take some examples: The nature of the reaction in the electrolyte solution is the reaction between ions?

Solution:

Example 1: AgNO3 + NaCl → AgCl ↓ + NaNO3

AgNO3, NaCl, Nano3 are strong electrolytes in the solution, they dissipate into ions. We have the ion equation:

Ag + + NO3- + Na + + Cl- → AgCl ↓ + NO3- + Na +

So in fact, the solution only has the reaction of:

Ag + + Cl- → AgCl ↓

The NO3-and Na+ ions still exist in the solution before and after the reaction.

Example 2: Na2SO3 + 2HCl → 2 NaCl + H2O + SO2 ↑

Na2SO3, HCl, and NaCl are strong electrolytes in the solution, they dissolve into ions. We have the ion equation:

2NA + + SO32- + 2H + + 2Cl- → 2NA + + 2Cl- + H2O + SO2 ↑

2H + + SO32- → H2O + SO2 ↑

So in fact, the solution has only the reaction of 2h+ and SO32-. The Na+ and Cl- ions still exist in the solution before and after the reaction. In essence, the reactions in the electrolyte solution are the reaction between ions because the electrolytes have dissociated into ions.

Lesson 4 Page 20 Chemistry 11 SGK

The shortened ion equation of the reaction indicates:

A. Which ions exist in the solution.

B. The concentration of the ions in the solution is the largest.

C. The nature of the reaction in the solution of electrolytes.

D. There is no molecular exist in the solution of electrolytes.

Solution: Answer C. Because this answer indicates which ion has worked with each other, causing the reaction to occur.

Lesson 5 chemistry 11 textbook page 20

Write the molecular equation and the shortened ion equation of the reactions (if any) occurs in the solution between the following pairs of substances:

a. Fe2 (SO4) 3 + NaOH

b. NH4Cl + AgNO3

c. NAF + HCl

d. MgCl2 + KNO3

e. Fes (r) + 2HCl

g. HCLO + KOH

Solution:

a. Fe2 (SO4) 3 + 6naoh → 3 Na2SO4 + 2Fe (OH) 3 ↓

Fe3 + + 3OH- → Fe (OH) 3 ↓

b. NH4Cl + AgNO3 → NH4NO3 + AgCl ↓

Ag + + Cl- → AgCl ↓

c. NAF + HCl → NaCl + HF

H++ F+ → HF

d. MgCl2 + KNO3 → No reaction

e. Fes (R) + 2HCl → FeCl2 + H2S ↑

Fes (r) + 2h + → Fe2 + + H2S ↑

g. HCLO + KOH → KCLO + H2O

HCLO + OH- → H2O + chlorine-

Solving 6th grade 11 textbook page 20

Which of the following reactions occurs in Fe (OH) 3 precipitate?

A. FeSO4 + KMnO4 + H2SO4

B. Fe2 (SO4) 3 + KI

C. Fe (NO3) 3 + Fe

D. Fe (NO3) 3 + KOH

Solution: Answer D.

Because: Fe (NO3) 3 + 3KOH → Fe (OH) 3 ↓ + 3kno3

Hopefully, through this knowledge, readers understand what the ion exchange reaction is, what is the condition of the reaction and writing the ionic equation is proficient. Do not forget to visit Mầm non Cát Linh every day to not miss many other interesting lessons about Chemistry! Wish you good study.

References

History, Introduction, and Kinetics of Ion Exchange Materials – Accessed date: July 17, 2022

https://www.hindawi.com/journals/jchem 2013/957647/

Ion Exchange – Accessed date: July 17, 2022

https://en.wikipedia.org/wiki/ion_exchange

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