Acid-Base Theory Quiz
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Questions and Answers

What best describes an amphiprotic species?

  • A species that can act only as an acid.
  • A species that can act as either an acid or a base. (correct)
  • A species that can act only as a base.
  • A species that cannot donate or accept protons.

Lewis acids are defined as substances that can accept protons.

False (B)

Give two examples of Lewis bases.

Ammonia (NH3) and water (H2O)

The formula for calculating pH from the concentration of hydrogen ions, [H+], is ______.

<p>-log[H+]</p> Signup and view all the answers

Match the following compounds with their classification as Arrhenius acid or base:

<p>HCl = Arrhenius acid NaOH = Arrhenius base NH3 = Cannot be classified H2SO4 = Arrhenius acid</p> Signup and view all the answers

What is the conjugate base of H2PO4−?

<p>HPO4²− (A)</p> Signup and view all the answers

HCl is considered a weak acid.

<p>False (B)</p> Signup and view all the answers

In the reaction NH3 + H2PO4− ⇌ NH4+ + HPO4²−, what role does NH3 play?

<p>base</p> Signup and view all the answers

The reaction of HCl with H2PO4− results in the formation of ______ and H3PO4.

<p>Cl−</p> Signup and view all the answers

Match the acid-base pairs with their respective classifications:

<p>HCl = Strong Acid CH3COOH = Weak Acid Cl− = Weak Base CH3COO− = Strong Base</p> Signup and view all the answers

Which statement correctly describes the relationship between a strong acid and its conjugate base?

<p>A strong acid has a weak conjugate base. (A)</p> Signup and view all the answers

What ions are formed during the auto ionization of water?

<p>H+ and OH−</p> Signup and view all the answers

Which of the following is an amphiprotic species?

<p>H2O (D)</p> Signup and view all the answers

All Brønsted-Lowry acids are also Lewis acids.

<p>True (A)</p> Signup and view all the answers

What is the self-ionization of ammonia?

<p>NH3 + NH3 ⇌ NH4+ + NH2-</p> Signup and view all the answers

According to the Lewis definition, an acid is any species that accepts an __________ pair to form a bond.

<p>electron</p> Signup and view all the answers

Which of the following pairs demonstrates a correct Lewis acid-base reaction?

<p>BF3 + NH3 (B)</p> Signup and view all the answers

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

<p>It only describes proton transfer reactions.</p> Signup and view all the answers

Which group contains the strongest acid?

<p>HClO4 (C)</p> Signup and view all the answers

Amphiprotic species can only donate protons.

<p>False (B)</p> Signup and view all the answers

Match the following species with their type:

<p>HCl = Strong Acid NH3 = Lewis Base OH- = Brønsted-Lowry Base H2O = Amphiprotic</p> Signup and view all the answers

Lewis acids accept __________ to form bonds.

<p>electron pairs</p> Signup and view all the answers

What is the correct expression for the acid-dissociation constant (Ka) for a weak acid (HA)?

<p>$K_a = \frac{[H_3O^+][A^-]}{[HA]}$ (D)</p> Signup and view all the answers

Weak acids have higher Ka values compared to strong acids.

<p>False (B)</p> Signup and view all the answers

What does the symbol Ka represent in acid-base chemistry?

<p>The acid-dissociation constant</p> Signup and view all the answers

The ionization constant of _____ acid is represented in the table.

<p>weak monoprotic</p> Signup and view all the answers

Match the following weak acids with their corresponding Ka values:

<p>Acetic acid = 1.8 × 10–5 Formic acid = 1.7 × 10–4 Hydrocyanic acid = 4.9 × 10–10 Hydrofluoric acid = 6.8 × 10–4</p> Signup and view all the answers

Which weak acid has the highest Ka value based on the provided data?

<p>Formic acid (D)</p> Signup and view all the answers

The concentration of water in the acid-dissociation constant expression is constant.

<p>True (A)</p> Signup and view all the answers

List one characteristic of weak acids.

<p>They partially ionize in water.</p> Signup and view all the answers

The numerical value of _____ is a reflection of the strength of the acid.

<p>Ka</p> Signup and view all the answers

Flashcards

Amphiprotic Species

A substance that can act as both an acid and a base, donating or accepting protons (H+).

Lewis Acid

A substance that can accept a pair of electrons to form a covalent bond.

Lewis Base

A substance that can donate a pair of electrons to form a covalent bond.

pH Calculation

Calculating pH from H+ concentration, or vice versa. Similarly for pOH from OH- concentration.

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Arrhenius Acid

A substance that increases the concentration of H+ ions in an aqueous solution.

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Brønsted-Lowry Acid

A substance that donates a proton (H+).

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Brønsted-Lowry Base

A substance that accepts a proton (H+).

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Conjugate Acid

The species formed when a base accepts a proton.

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Conjugate Base

The species formed when an acid loses a proton.

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Strong Acid

An acid that completely dissociates in water to release H+ ions.

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Strong Base

A base that completely accepts protons from water, dissociating completely.

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Autoionization of Water

The reaction of two water molecules forming a hydroxide ion and a hydronium ion.

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H2PO4- is amphiprotic

H2PO4- can act as an acid by donating a proton to form HPO42-, and it can act as a base by accepting a proton to form H3PO4.

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H2O is amphiprotic

Water can act as an acid by donating a proton to form OH-, and it can act as a base by accepting a proton to form H3O+.

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Strongest base? (OH-, Cl-, NO2-, CH3COO-, NH3)

OH- is the strongest base in the given group. Bases accept protons. Hydroxide readily accepts protons.

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Strongest acid? (HClO4, CH3COOH, HNO3, HCl)

HClO4 (perchloric acid) is the strongest acid in the group. Acids donate protons. Perchloric acid readily ionizes to donate H+.

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Brønsted-Lowry Theory Weakness

The Brønsted-Lowry theory focuses solely on proton transfer and cannot explain acid-base reactions in non-aqueous solvents.

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Self-ionization of Ammonia

2NH3(l) ⇌ NH4+(am) + NH2-(am)

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Lewis Acid-Base vs. Brønsted-Lowry

Lewis definition is broader, including electron pair donation/acceptance. Brønsted-Lowry only deals with proton transfer.

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Are ALL Brønsted-Lowry acids/bases Lewis acids/bases?

Yes, all Brønsted-Lowry acids/bases are also Lewis acids/bases. Proton transfer involves electron pair movement.

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Weak Acid

An acid that only partially ionizes in water, meaning it doesn't completely donate all its protons (H+).

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Acid Dissociation Constant (Ka)

A measure of the strength of a weak acid. It represents the equilibrium constant for the ionization of the acid in water.

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What does a higher Ka value mean for an acid?

A higher Ka value indicates a stronger acid, meaning it ionizes to a greater extent in water, releasing more H+ ions.

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Equilibrium Constant Expression for Weak Acid

The ratio of the product of the concentrations of the hydronium ions (H3O+) and the conjugate base (A-) to the concentration of the undissociated acid (HA).

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Why is water's concentration not included in Ka?

The concentration of water in dilute solutions is nearly constant and doesn't significantly change during the ionization process.

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How is Ka related to the strength of an acid?

A higher Ka value indicates a stronger acid, as it ionizes to a greater extent, generating more H+ ions.

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Monoprotic Acid

An acid that can donate only one proton (H+) per molecule when dissolved in water.

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Ionization of Weak Acid

The process where a weak acid partially donates protons (H+) to water molecules, forming hydronium ions (H3O+) and the conjugate base of the acid.

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What does the table of ionization constants indicate?

The table shows the Ka values for various weak monoprotic acids. It highlights the relative strengths of these acids based on their respective Ka values.

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