AP Chemistry:: Acids Bases

What is the BRONSTED-LOWRY definition of an ACID and a BASE?

- **A)** Bronsted-Lowry acids and bases are defined only by their COLOR change with an indicator, with no relationship to protons
- **B)** A BRONSTED-LOWRY ACID is a PROTON (H+) DONOR, while a BRONSTED-LOWRY BASE is a PROTON ACCEPTOR
- **C)** This definition has no actual relationship to proton donation or acceptance
- **D)** A Bronsted-Lowry acid is a proton ACCEPTOR, while a Bronsted-Lowry base is a proton DONOR (the reverse of the actual definitions)

What is a CONJUGATE ACID-BASE PAIR, and how do the two members of such a pair DIFFER from each other STRUCTURALLY?

- **A)** Two species that differ from each other by EXACTLY ONE PROTON (H+) -- when an acid donates its proton, it becomes its CONJUGATE BASE; when a base accepts a proton, it becomes its CONJUGATE ACID
- **B)** A conjugate acid-base pair refers to two COMPLETELY UNRELATED substances, with no structural connection between them
- **C)** This concept has no actual relationship to two species differing from each other by a single proton
- **D)** The two members of a conjugate pair always differ by TWO protons, rather than exactly one

In the reaction 'HCl + H2O -> H3O+ + Cl-', identify the CONJUGATE BASE of HCl.

- **A)** H3O+ is the conjugate base of HCl, rather than Cl- (incorrectly identifying the conjugate acid of water as HCl's conjugate base)
- **B)** Cl- is the conjugate base of HCl, since HCl DONATED a proton (H+) to become Cl-, differing by exactly one proton
- **C)** H2O is the conjugate base of HCl, despite H2O not actually being derived from HCl losing a proton
- **D)** This reaction has no actual relationship to identifying conjugate acid-base pairs

What is an AMPHOTERIC (or amphiprotic) substance, and why is WATER (H2O) a classic example of one?

- **A)** Water is amphoteric because it always acts as a NEUTRAL spectator, never actually donating or accepting any proton
- **B)** An amphoteric substance can ONLY ever act as an acid, never as a base, contradicting the actual definition
- **C)** A substance that can act as EITHER an ACID (donating a proton) OR a BASE (accepting a proton), depending on what it reacts with; water is amphoteric because it can donate a proton (becoming OH-) or accept one (becoming H3O+)
- **D)** This concept has no actual relationship to a substance being capable of acting as both an acid and a base

What is AUTOIONIZATION OF WATER, and what does the resulting equilibrium constant Kw (at 25°C, Kw = 1.0 x 10^-14) represent?

- **A)** This concept has no actual relationship to water molecules reacting with each other to produce H3O+ and OH- ions
- **B)** Autoionization of water refers to water molecules reacting with an EXTERNAL acid or base, rather than with each other
- **C)** The process by which water molecules react with EACH OTHER (one acting as acid, one as base) to form a small amount of H3O+ and OH- ions; Kw is the equilibrium constant for this reaction, equal to [H3O+][OH-]
- **D)** Kw represents the concentration of PURE water molecules only, with no relationship to H3O+ or OH- ion concentrations

What is the mathematical relationship between [H3O+] and [OH-] in ANY aqueous solution at 25°C, based on the Kw constant?

- **A)** [H3O+] x [OH-] = Kw = 1.0 x 10^-14 at 25°C -- this relationship holds true for ANY aqueous solution (acidic, neutral, or basic), not just pure water
- **B)** This relationship has no actual mathematical connection between [H3O+] and [OH-] in an aqueous solution
- **C)** [H3O+] and [OH-] are always exactly EQUAL to each other in every aqueous solution, regardless of whether the solution is acidic, neutral, or basic
- **D)** [H3O+] x [OH-] always equals ZERO in any solution other than pure water

What is the PH SCALE, and how is pH mathematically defined in terms of [H3O+] concentration?

- **A)** A logarithmic scale used to express a solution's acidity; pH = -log[H3O+] -- as [H3O+] increases (solution becomes MORE acidic), pH DECREASES
- **B)** As [H3O+] increases, pH also INCREASES, the reverse of the actual inverse relationship between these two quantities
- **C)** This scale has no actual mathematical relationship to a solution's [H3O+] concentration
- **D)** pH is defined as the DIRECT (non-logarithmic) value of [H3O+] concentration, with no logarithm involved in the calculation

What pH VALUE is considered NEUTRAL at 25°C, and what does this specific value represent about the relative concentrations of [H3O+] and [OH-] in a neutral solution?

- **A)** Neutral pH represents a solution where [H3O+] is much GREATER than [OH-], rather than the two being equal
- **B)** A pH of 0 is considered neutral, rather than 7.0, misrepresenting the actual neutral point on the pH scale
- **C)** A pH of 7.0 is considered neutral at 25°C, representing a solution where [H3O+] EQUALS [OH-] (both equal to 1.0 x 10^-7 M)
- **D)** This concept has no actual relationship to a specific pH value representing equal [H3O+] and [OH-] concentrations