AP Chemistry acids and buffers review

What defines a strong acid?

A strong acid completely dissociates in water, producing H+ ions.

True or false: Acetic acid is a strong acid.

False, because acetic acid is a weak acid.

Difference between strong and weak acids.

Strong acids fully dissociate, while weak acids partially dissociate in solution.

What is a buffer solution?

A buffer solution resists changes in pH upon the addition of small amounts of acid or base.

Fill the blank: The pH of a neutral solution at 25°C is _____ .

7.0

Question: How does a buffer work?

A buffer contains a weak acid and its conjugate base to neutralize added acids or bases.

What is the Henderson-Hasselbalch equation?

The equation is $\displaystyle pH = pK_a + \log{\\frac{[A^-]}{[HA]}}$.

True or false: NH4Cl is a buffer.

False, because it does not contain a weak acid and its conjugate base.

What happens when you add strong acid to a buffer?

The weak base in the buffer reacts with the added H+, minimizing pH change.

Identify a characteristic of weak acids.

Weak acids have a pKa greater than 0 and do not fully dissociate.

Comparison: pH and pKa.

pH measures acidity; pKa is the acid dissociation constant, indicating strength.

What does the term 'conjugate base' mean?

The species that remains after an acid donates a proton (H+).

Fill the blank: The conjugate base of HCl is _____ .

Cl-

Question: How does adding a strong base to a buffer affect it?

The weak acid in the buffer reacts with the base, stabilizing pH.

Define the term 'acid dissociation constant' (Ka).

Ka quantifies the strength of an acid in solution; higher Ka indicates stronger acid.

What is the relationship between pKa and acid strength?

Lower pKa values correspond to stronger acids.

True or false: Buffers can only be made from weak acids.

True, because buffers require a weak acid and its conjugate base.

Fill the blank: The pH of a solution can be calculated from the concentration of _____ .

Hydronium ions, H3O+.

Question: What role does the conjugate acid play in buffering?

It neutralizes added bases, maintaining the pH of the solution.

Comparison: Strong vs. weak base.

Strong bases fully dissociate; weak bases do not.

What does it mean for an acid to be diprotic?

A diprotic acid can donate two protons (H+) per molecule.