Chemistry: Arrhenius Theory & Mass Action Law

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the concentration of H+ ions in pure water?

10-9 mole

10-8 mole

10-7 mole (correct)

10-6 mole

What does a larger K₂ value indicate about an acid?

Weaker acid

Stronger base

Neutral strength

Stronger acid (correct)

If the pH of a solution is less than 7, what can be inferred about the solution?

It is acidic (correct)

It is neutral

It is alkaline

It has a higher concentration of OH- ions

How is the relationship between pKa and acid strength characterized?

Higher pKa indicates weaker acid (D) Signup and view all the answers

What is the formula to calculate pOH from pH?

pOH = 14 - pH (D) Signup and view all the answers

When the concentration of H+ ions is greater than 10-7, how is the solution classified?

Acidic (C) Signup and view all the answers

What does an increase in Ka imply about an acid?

It is strengthening (A) Signup and view all the answers

Which statement is true about pH and pKa?

pH measures ion concentration; pKa measures dissociation strength (A) Signup and view all the answers

Which substances are classified as non-electrolytes?

Alcohols and glucose (B) Signup and view all the answers

For a strong electrolyte, the degree of dissociation (α) is approximately equal to which value?

1 (D) Signup and view all the answers

What does the degree of dissociation (α) indicate?

The extent to which electrolyte molecules split into ions (A) Signup and view all the answers

What is the dissociation equation for hydrochloric acid (HCl) in water?

HCl → H+ + Cl- (C) Signup and view all the answers

According to the law of mass action, which equation defines the equilibrium constant (K)?

K = [C][D] / [A][B] (C) Signup and view all the answers

Which of the following statements is true regarding the dissociation of water?

Water ionizes to a very small extent. (D) Signup and view all the answers

What does the symbol K represent in the context of chemical reactions?

Equilibrium constant (C) Signup and view all the answers

If the degree of dissociation (α) is 60%, what does this imply?

60% of the molecules have dissociated into ions. (B) Signup and view all the answers

What is the pH of a completely ionized 1.0 N solution of hydrochloric acid?

0 (A) Signup and view all the answers

For a solution of 0.009 N hydrochloric acid, what is the pH?

2.05 (D) Signup and view all the answers

How is the pH of a weak acid, like acetic acid, calculated?

pH = ½ (pKa + pCa) (D) Signup and view all the answers

What would be the pH of a 0.0045 M solution of phenobarbital with a pK of 7.41?

4.88 (C) Signup and view all the answers

Calculate the pH of a 0.13 N ammonia solution with a pK of 4.76.

11.18 (A) Signup and view all the answers

What is the hydroxyl ion concentration of a solution with a pH of 10.75?

5.62 x 10^-4 M (D) Signup and view all the answers

If the pH of a solution is 5.3, what is the hydrogen ion concentration?

5.01 x 10^-6 M (D) Signup and view all the answers

A salt formed from a strong acid and a strong base typically has what pH?

pH = 7 (D) Signup and view all the answers

What is hydrolysis in the context of salts?

The reaction of an ion with water to produce conjugate acids and bases. (B) Signup and view all the answers

Which condition results in a salt solution having a pH less than 7?

Salt derived from a strong acid and a weak base. (B) Signup and view all the answers

In the context of ammonia chloride (NH4Cl), which statement is correct regarding its hydrolysis?

It results in the generation of H+ ions, leading to an acidic solution. (A) Signup and view all the answers

What determines the pH level of a salt solution?

The strengths of the acids and bases from which the salt is derived. (D) Signup and view all the answers

How do you calculate the percentage of salt hydrolyzed in solution?

100 x (y/Cs) (B) Signup and view all the answers

Given a 0.1 M sodium acetate solution with a pK of 4.76, what is the calculated pH?

8.88 (A) Signup and view all the answers

In the context of salts, what is the degree of hydrolysis?

The fraction of total salt that undergoes hydrolysis at equilibrium. (A) Signup and view all the answers

What is the expected pH for a salt formed from a weak acid and a weak base?

pH is indeterminate without more information. (B) Signup and view all the answers

Study Notes

Arrhenius Theory of Ionization/Dissociation

Electrolytes dissociate into oppositely charged ions when dissolved in water.
Non-electrolytes do not ionize at all in solution.
Degree of Dissociation (α): The fraction of molecules that dissociate into ions; expressed as a percentage.
- α = (number of molecules dissociated / total number of molecules) x 100%
Strong Electrolytes (Strong acids and bases) have α close to 1.
Weak Electrolytes (Weak acids and bases) have α less than 1.

Law of Mass Action

The rate of a chemical reaction is proportional to the active masses of the reacting substances.
Equilibrium Constant (K): Ratio of product concentrations to reactant concentrations at equilibrium.
- K = [C][D] / [A][B]
Dissociation of Water:
- Water is a weak electrolyte, H₂O ↔ H+ + OH-
- Ionic Product of Water (Kw): [H+][OH-] = 10⁻¹⁴
- pH Scale:
 - pH = -log[H⁺], pOH = -log[OH⁻]
 - pKw = pH + pOH = 14
 - Neutral:[H+] = [OH-] = 10⁻⁷
 - Acidic: [H+] > 10⁻⁷
 - Alkaline (Basic): [H+] < 10⁻⁷

Dissociation of Acids and Bases

Weak Acids: HA + HOH <=> H3O+ + A-
- Ka: Acid ionization constant, K = [H+][A-] / [HA]
Weak Bases: B + HOH <=> BH+ + OH-
- Kb: Base ionization constant, K = [BH+][OH-] / [B]
pKa and pKb: Relate to the strength of acids and bases:
- pKa = -logKa, pKb = -logKb
- Larger Ka (smaller pKa) = Stronger acid
- Larger Kb (smaller pKb) = Stronger base

Importance of Dissociation Constants

Ka and Kb values determine the strength of acids and bases.
pH Calculations:
- Strong Acid: pH = -log [H+], pH = pC₂ (concentration of acid)
- Strong Base: pH = pKw - pCb (concentration of base)
- Weak Acid: pH = ½ (pKa + pCa)
- Weak Base: pH = pKw - ½ (pKb + pCb)
Salts:
- Neutral Salt: Formed by the reaction of a strong acid and a strong base, pH = 7.
- Basic Salt: Formed by the reaction of a weak acid and a strong base, pH > 7.
- Acidic Salt: Formed by the reaction of a strong acid and a weak base, pH < 7.
- Salt of Weak Acid & Weak Base: pH = 0.5 (pKa + pKb - pCs)
Degree of Hydrolysis (h): The fraction of salt hydrolyzed at equilibrium.
- h = (concentration of hydrolyzed species) / (concentration of salt)
- % hydrolysis = 100 x h
Remember:*
pKa gives information about the acid's dissociation in water; pH gives information about the H+ concentration in solution.
The stronger the acid or base, the higher the Ka or Kb values, and the lower the pKa or pKb values.
The pH of a salt solution depends on the strengths of the original acid and base that formed it.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers essential concepts from the Arrhenius Theory of Ionization/Dissociation and the Law of Mass Action. Learn about electrolytes, the degree of dissociation, and the equilibrium constant. Test your knowledge on these fundamental principles of chemistry.