Podcast
Questions and Answers
What type of reaction is the interaction between a salt and water, leading to the formation of an acidic or basic solution?
What type of reaction is the interaction between a salt and water, leading to the formation of an acidic or basic solution?
- Esterification
- Saponification
- Neutralization
- Hydrolysis (correct)
Which of the following salt solutions will have a pH close to 7?
Which of the following salt solutions will have a pH close to 7?
- A salt derived from a weak base and a weak acid.
- A salt derived from a strong base and a weak acid
- A salt derived from a weak base and a strong acid
- A salt derived from a strong base and a strong acid (correct)
If a salt undergoes hydrolysis and the resulting solution has a pH > 7, what can be inferred about the strength of the acid and base that formed the salt?
If a salt undergoes hydrolysis and the resulting solution has a pH > 7, what can be inferred about the strength of the acid and base that formed the salt?
- The salt is formed from a weak acid and a weak base.
- The salt is formed from a strong acid and a strong base.
- The salt is formed from a strong acid and a weak base.
- The salt is formed from a weak acid and a strong base. (correct)
Which of the following is the correct representation of the hydrolysis of $NH_4Cl$?
Which of the following is the correct representation of the hydrolysis of $NH_4Cl$?
What effect does the hydrolysis of $CH_3COO^−$ ions have on the pH of a solution?
What effect does the hydrolysis of $CH_3COO^−$ ions have on the pH of a solution?
When $NaHCO_3$ is dissolved in water, which reaction primarily occurs?
When $NaHCO_3$ is dissolved in water, which reaction primarily occurs?
In the context of salt hydrolysis, what does a 'stepwise' process refer to?
In the context of salt hydrolysis, what does a 'stepwise' process refer to?
Why is the second step of hydrolysis for a salt like $Na_2CO_3$ less significant than the first?
Why is the second step of hydrolysis for a salt like $Na_2CO_3$ less significant than the first?
If the base dissociation constant ($K_b$) of an ion is significantly greater than the acid dissociation constant ($K_a$) of its conjugate acid, what can be predicted about the pH of the solution?
If the base dissociation constant ($K_b$) of an ion is significantly greater than the acid dissociation constant ($K_a$) of its conjugate acid, what can be predicted about the pH of the solution?
A solution of $NH_4NO_3$ is tested with an indicator and found to be acidic. Which ion from the salt is primarily responsible for this?
A solution of $NH_4NO_3$ is tested with an indicator and found to be acidic. Which ion from the salt is primarily responsible for this?
What does the process of neutralization involve?
What does the process of neutralization involve?
When $NH_3(aq)$ reacts with $CH_3COOH(aq)$, what determines whether the resulting solution's pH is above or below 7?
When $NH_3(aq)$ reacts with $CH_3COOH(aq)$, what determines whether the resulting solution's pH is above or below 7?
A solution of $KCl$ is tested for its impact on litmus paper. What would you expect to observe?
A solution of $KCl$ is tested for its impact on litmus paper. What would you expect to observe?
In a solution of potassium acetate ($CH_3COOK$), which ion is primarily responsible for increasing the pH?
In a solution of potassium acetate ($CH_3COOK$), which ion is primarily responsible for increasing the pH?
Which of the following reactions represents the hydrolysis of the ammonium ion?
Which of the following reactions represents the hydrolysis of the ammonium ion?
If $K_b$ for $NH_3$ is $1.8 \times 10^{-5}$, and $K_a$ for acetic acid ($CH_3COOH$) is $1.8 \times 10^{-5}$, what is the approximate pH of a solution of $CH_3COONH_4$?
If $K_b$ for $NH_3$ is $1.8 \times 10^{-5}$, and $K_a$ for acetic acid ($CH_3COOH$) is $1.8 \times 10^{-5}$, what is the approximate pH of a solution of $CH_3COONH_4$?
Why do salts formed from strong acid-strong base pairs not undergo hydrolysis??
Why do salts formed from strong acid-strong base pairs not undergo hydrolysis??
The hydrolysis of sodium carbonate ($Na_2CO_3$) leads to what kind of solution?
The hydrolysis of sodium carbonate ($Na_2CO_3$) leads to what kind of solution?
The concentration of which ions determines whether a solution is acidic or basic during hydrolysis?
The concentration of which ions determines whether a solution is acidic or basic during hydrolysis?
Why are salts of weak acids and weak bases more complex to analyze regarding their pH compared to salts of strong acids and bases?
Why are salts of weak acids and weak bases more complex to analyze regarding their pH compared to salts of strong acids and bases?
Flashcards
Salt Hydrolysis
Salt Hydrolysis
The reaction of salt ions with water, affecting the solution's pH.
Neutralization
Neutralization
A reaction where an acid and base neutralize each other, forming a salt and water.
Strong acid and strong base
Strong acid and strong base
No hydrolysis occurs; pH remains neutral (pH=7).
Strong base and weak acid
Strong base and weak acid
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Weak base and strong acid
Weak base and strong acid
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Weak base and weak acid
Weak base and weak acid
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Hydrolysis of weak acid salt
Hydrolysis of weak acid salt
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Hydrolysis of weak base salt
Hydrolysis of weak base salt
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Stepwise Hydrolysis
Stepwise Hydrolysis
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Hydrolysis Constant (Kb)
Hydrolysis Constant (Kb)
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pH Scale
pH Scale
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Acidic Solution
Acidic Solution
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Basic Solution
Basic Solution
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Study Notes
- The topic is Salt Hydrolysis.
Material
- The material is for 4th grade.
- The material comes from textbook pages 251-253.
Learning Content
- Expand knowledge about aqueous solutions of salts.
- Determine the pH of different salt solutions practically using a sensor and/or a universal indicator.
- Learn to explain and write hydrolysis equations for the reaction of weak acid residue ions (carbonate, ethanoate) with water, indicating that the medium of these salt solutions is basic.
- Discuss the importance of hydrogen ion concentration for vital processes.
Salt production
- Salts are produced by neutralization.
- KOH(aq) + HCl(aq) → NaCl(aq) + H2O(s): A salt obtained by reacting a strong base and acid does not hydrolyze; the pH of the resulting solution equals 7.
- KOH(aq) + CH3COOH(aq) → CH3COOK(aq) + H2O(s): A salt obtained by reacting a strong base and a weak acid hydrolyzes; the pH of the resulting solution is greater than 7.
- NH3(aq) + HCl(aq) → NH4Cl(aq): A salt obtained by reacting a weak base and strong acid hydrolyzes; the pH of the resulting solution is less than 7.
- NH3(aq) + CH3COOH(aq) → CH3COONH4(aq): If a salt is formed by reacting a weak base and acid, both ions participate in the hydrolysis.
- The solution's pH is close to 7 if the base's Kb is approximately equal to the acid's Ka.
- The solution's pH is greater than 7, if the base's Kb is greater than the acid's Ka.
- The solution's pH is less than 7, if the base's Kb is less than the acid's Ka.
Salt Hydrolysis (Weak Acid)
- CH3COOK is an ionic compound, so only ions are in the solution: CH3COOK(aq) → CH3COO-(aq) + K+(aq).
- Ethanoate CH3COO- ions interact with H2O molecules; part of the ethanoate ions take a proton from the H2O molecules: CH3COO-(aq) + H2O(s) ⇄ CH3COOH(aq) + OH-(aq).
- Potassium ethanoate hydrolysis equation: CH3COOK(aq) + H2O(s) ⇄ CH3COOH(aq) + KOH(aq).
- The medium is basic.
- It is a reversible exchange reaction between salt and water.
- This reaction occurs because a weak electrolyte, ethanoic acid, is formed.
- Water is an even weaker electrolyte, so the equilibrium shifts to the left, and only a small portion of the salt hydrolyzes.
- Enough of the salt is hydrolyzed to make the resulting solution basic due to an increase in OH-(aq) concentration.
Salt Hydrolysis (Weak Base)
- NH4Cl is an ionic compound, so only ions are present in the solution: NH4Cl(aq) → NH4+(aq) + Cl-(aq).
- Ammonium NH4+ ions interact with H2O molecules: NH4+(aq) + H2O(s) ⇄ NH3(aq) + H3O+(aq).
- Ammonium chloride hydrolysis equation: NH4Cl(aq) + H2O(s) ⇄ NH4OH(aq) + HCl(aq).
- The medium is acidic.
- The resulting solution becomes acidic because the concentration of H3O+(aq) increases.
Stepwise salt hydrolysis
- Sodium carbonate is an ionic compound, so only ions are present in the solution: Na2CO3(aq) → 2Na+(aq) + CO32-(aq).
- Carbonate ions are remnants of a weak acid so, the resulting solution will be basic.
- The carbonate ion's charge is 2-, so hydrolysis occurs in two steps: CO32-(aq) + H2O(s) ⇄ HCO32-(aq) + OH-(aq).
- The yield is largest in the first step.
- A second step may occur: HCO3-(aq) + H2O(s) ⇄ H2CO3(aq) + OH-(aq).
- The yield in the second step is negligibly small.
- The second step almost doesn't happen.
- In the first step, OH- ions are formed, which inhibits further hydrolysis.
- Thus, the concentration of H2CO3 is negligibly small, so the typical decomposition of H2CO3 does not occur, and no CO2 is formed.
- If NaHCO3 is dissolved, only reaction (3) occurs and the basic properties of this solution are less pronounced.
Calculating the pH of Salt Solutions
- Potassium ethanoate hydrolysis reactions: CH3COO-(aq) + H2O(s) ⇄ CH3COOH(aq) + OH-(aq).
- The equilibrium constant Kb = 5.71 x 10^-10.
- Use Kb, to calculate the formula for the potassium ethanoate hydrolysis constant
- C(CH3COOH) = √c(CH3COO−) • K₁ = √0.10 x 5.71 x 10^-10 = 7.6 x 10^-6mol/l, to calculate the molar concentration of ethane molecules in a 0.10 mol/l potassium ethanoate solution.
- The concentration of (OH-) = 7.6 x 10^-6 mol/l to calculate the pH of the solution.
- Concentration of (H+) = Kw/c(OH-) = 1.0 x 10^-14 / 7.6 x 10^-6 = 1.33 x 10^-9 mol/l.
- pH = −1g(cH+) = -lg(1,33 x 10^-9) = 8.88.
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