In acid-base chemistry, what does pKa represent?

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards
From $25.99Unlock all

Study for the Honors Chemistry Exam with flashcards and multiple choice questions. Enhance your understanding with detailed explanations and hints. Prepare to excel in your exam!

Multiple Choice

In acid-base chemistry, what does pKa represent?

Explanation:
pKa is the pH where the acid is half dissociated. For an acid HA ⇌ H+ + A−, Ka = [H+][A−]/[HA], and pKa = −log Ka. When half of the acid has donated its proton, [HA] equals [A−], which makes [H+] equal to Ka, so the pH equals pKa. This also explains why pKa reflects acid strength: smaller pKa means the acid dissociates more in solution. The Henderson–Hasselbalch form, pH = pKa + log([A−]/[HA]), shows that when the two forms are in equal amounts, pH equals pKa. The other statements don’t describe pKa: fully dissociated is a different condition, pH of pure solvent isn’t pKa, and pKa is not the negative log of the base dissociation constant (that would be pKb).

pKa is the pH where the acid is half dissociated. For an acid HA ⇌ H+ + A−, Ka = [H+][A−]/[HA], and pKa = −log Ka. When half of the acid has donated its proton, [HA] equals [A−], which makes [H+] equal to Ka, so the pH equals pKa. This also explains why pKa reflects acid strength: smaller pKa means the acid dissociates more in solution. The Henderson–Hasselbalch form, pH = pKa + log([A−]/[HA]), shows that when the two forms are in equal amounts, pH equals pKa. The other statements don’t describe pKa: fully dissociated is a different condition, pH of pure solvent isn’t pKa, and pKa is not the negative log of the base dissociation constant (that would be pKb).

More Multiple Choice Questions
Subscribe

Get the latest from Passetra

You can unsubscribe at any time. Read our privacy policy