Chem Test 3 Brønsted-Lowry Acid-Base Theory

What is a Brønsted-Lowry acid?

A proton (H⁺) donor.

What is a Brønsted-Lowry base?

A proton (H⁺) acceptor.

What happens to HA when it donates H⁺?

It becomes A⁻, its conjugate base.

What happens to B when it accepts H⁺?

It becomes HB⁺, its conjugate acid.

What do conjugate acid-base pairs differ by?

Exactly one proton (H⁺).

How does the Brønsted-Lowry theory relate to Arrhenius theory?

Brønsted-Lowry includes Arrhenius as a special case and works even when water isn't present.

What is the role of water in the reaction of HCl with water?

Water acts as a base and accepts the proton.

What is the role of water in the reaction of NH₃ with water?

Water acts as an acid and donates the proton.

What is an amphoteric substance?

A substance that can act as either an acid or a base, like water.

List the strong acids.

HCl, HBr, HI, H₂SO₄, HNO₃, HClO₄.

List the strong bases.

LiOH, NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂.

What is a key consequence of strong acids?

Their conjugate bases are extremely weak/inert.

What trend affects the strength of binary acids down a group?

Acidity generally increases because the H-A bond gets longer/weaker.

What trend affects the strength of binary acids across a period?

Higher electronegativity of A leads to stronger acids as H⁺ is easier to donate.

What factors influence the strength of oxoacids?

Electronegativity of X and the number of O atoms.

What is the autoionization of water?

H₂O + H₂O ⇌ H₃O⁺ + OH⁻.

What is the equilibrium expression for Kw?

Kw = [H₃O⁺][OH⁻].

What is the value of Kw at 25 °C?

1.0 × 10⁻¹⁴.

How do you determine if a solution is acidic, basic, or neutral using Kw?

Compare [H₃O⁺] and [OH⁻]: acidic if [H₃O⁺] > [OH⁻], basic if [H₃O⁺] < [OH⁻], neutral if [H₃O⁺] = [OH⁻].

How do you calculate [H₃O⁺] from [OH⁻]?

[H₃O⁺] = Kw / [OH⁻].

How do you calculate [OH⁻] from [H₃O⁺]?

[OH⁻] = Kw / [H₃O⁺].

What is the concentration of [H₃O⁺] in neutral water at 25 °C?

1.0 × 10⁻⁷ M.

What is the concentration of [OH⁻] in neutral water at 25 °C?

1.0 × 10⁻⁷ M.

What is the final value of Kw at 370 °C?

Approximately 1.8 × 10⁻⁹.

What is the Brønsted-Lowry definition of an acid?

An acid is a proton (H+) donor.

What is the Brønsted-Lowry definition of a base?

A base is a proton (H+) acceptor.

What is a conjugate acid-base pair?

A pair of species that differ by a proton; for example, HA and A−.

How does the Brønsted-Lowry definition relate to the Arrhenius definition?

The Brønsted-Lowry definition is more general and includes the Arrhenius definition as a special case.

What is an example of an amphoteric substance?

Water (H2O) can act as both an acid and a base.

What happens when hydrochloric acid (HCl) is added to water?

HCl donates a proton to water, forming hydronium ions (H3O+).

What is the difference between strong and weak acids?

Strong acids completely dissociate in solution, while weak acids only partially dissociate.

What is the significance of the dissociation of strong acids?

Strong acids dissociate almost completely, leading to a large equilibrium constant (Kc).

List three common strong acids.

HCl (hydrochloric acid), H2SO4 (sulfuric acid), HNO3 (nitric acid).

List three common strong bases.

NaOH (sodium hydroxide), KOH (potassium hydroxide), Ca(OH)2 (calcium hydroxide).

What is the conjugate base of hydrochloric acid (HCl)?

The conjugate base is Cl− (chloride ion).

What is the role of electronegativity in acid strength?

Higher electronegativity of the atom bonded to hydrogen increases acid strength due to easier proton donation.

What does it mean for an acid to be binary?

Binary acids consist of only two elements, typically hydrogen and a nonmetal.

What is an oxoacid?

An oxoacid contains hydrogen, oxygen, and another element, typically a nonmetal.

How does bond strength affect acid strength?

Stronger H-A bonds make it less likely for the acid to donate a proton, reducing acid strength.

What is the significance of the hydronium ion (H3O+) in acid-base reactions?

H3O+ represents a proton in aqueous solution and indicates the presence of an acid.

What is the relationship between strong acids and their conjugate bases?

The conjugate bases of strong acids are very weak and have little tendency to accept protons.

What is a strong electrolyte?

A substance that completely dissociates into ions in solution.

What does it mean for a substance to be inert in acid-base chemistry?

An inert substance has no tendency to participate in proton transfer reactions.

What is the general reaction format for Brønsted-Lowry acid-base reactions?

HA + B ⇌ A− + HB+ (where HA is the acid and B is the base).

What is the importance of the polarity of the H-A bond in acids?

Polarity influences the ability of the acid to donate a proton; more polar bonds are typically stronger acids.

What are the factors that affect acid strength?

Bond strength, bond polarity, and the stability of the conjugate base.

What is the role of water in Brønsted-Lowry acid-base reactions?

Water can act as a base by accepting protons or as an acid by donating protons.

How can you identify strong acids and bases?

By memorizing a list of common strong acids and bases provided in textbooks.

What is the significance of the term 'amphoteric'?

Amphoteric substances can act as both acids and bases depending on the reaction context.

What is the general trend for acid strength among binary acids?

Acid strength increases with the size of the atom bonded to hydrogen and its electronegativity.

What is a binary acid?

An acid that contains hydrogen and one other nonmetallic element.

How does atomic radius affect binary acid strength?

As you go down a group, the atomic radius increases, leading to longer and weaker H-A bonds, making the acid stronger.

What is the bond strength of H-F?

567 kJ mol-1

Which binary acid has the weakest bond strength?

H-I with a bond strength of 299 kJ mol-1.

What factor is more important for bond strengths across a period?

The electronegativity of the nonmetallic element.

Why is CH4 a poor acid?

The C-H bond is essentially non-polar, so there is little tendency for H to leave as H+.

What is the general form of an oxoacid?

HnXOm, where n and m are integers and X is a nonmetallic element.

How does electronegativity affect the strength of oxoacids with the same number of oxygen atoms?

Acid strength increases with the electronegativity of X, weakening the O-H bond.

What is the order of acid strength for H-O-X with different halogens?

H-O-Cl (weak) < H-O-Br (weaker) < H-O-I (weakest).

How does the number of oxygen atoms affect oxoacid strength?

For the same X, acid strength increases with the number of oxygen atoms.

What is the relative strength of HClO, HClO2, HClO3, and HClO4?

HClO (weaker) < HClO2 (weak) < HClO3 (strong) < HClO4 (stronger).

What is the equilibrium constant for the autoionization of water?

Kw = [H3O+][OH−] = 1.0 × 10−14 at 25 °C.

What does a tiny value of Kw indicate?

The equilibrium lies very far to the left, meaning almost none of the water is dissociated.

What defines an acidic solution in terms of H3O+ and OH− concentrations?

[H3O+] > [OH−].

What defines a basic solution in terms of H3O+ and OH− concentrations?

[H3O+] < [OH−].

What defines a neutral solution in terms of H3O+ and OH− concentrations?

[H3O+] = [OH−].

What is the concentration of H3O+ in pure, neutral water at 25 °C?

1.0 × 10−7 M.

What is the significance of the product of [H3O+] and [OH−]?

It is always equal to 1.0 × 10−14 at equilibrium at 25 °C.

What happens to the stability of the conjugate base with more oxygen atoms?

More resonance structures stabilize the conjugate base.

What is the relationship between bond strength and acid strength in oxoacids?

Weaker O-H bonds lead to stronger acids.

How does the polarity of the H-A bond affect acid strength?

Greater polarity increases the likelihood of H leaving as H+.

What is the role of hydrogen bonding in water's properties?

It explains water's unusual density and behavior as an acid and base.

What is the Brønsted-Lowry definition of acids and bases?

Acids donate H+ ions, while bases accept H+ ions.

What is the significance of the equilibrium constant expression for the autoionization of water?

It illustrates that both H3O+ and OH− are present in all aqueous solutions.

What is the effect of increasing electronegativity of X in oxoacids?

It increases acid strength by weakening the O-H bond.