pKa Values of Common Acids

Vocabulary flashcards covering common acid and conjugate base pairs, their pKa values, and relative acid/base strength trends.

Hydrochloric acid

A strong acid ($HCl$) with a $pK_a$ of $-7$ and a conjugate base of chloride ($Cl^-$).

Hydronium

$pK_a$ of $-1.7$

Acetic acid

An organic acid with a $pK_a$ of $4.8$ and a conjugate base of acetate.

Ammonium

An acidic cation ($H-NH_3^+$) with a $pK_a$ of $9.25$ and a conjugate base of ammonia ($NH_3$).

Ethanol

An alcohol acting as an acid with a $pK_a$ of $16$ and a conjugate base of ethoxide (alkoxide).

Ethyne (sp)

An alkyne ($H-C \equiv CH$) with a $pK_a$ of $25$ and a conjugate base of acetylide anion ($^-\!C \equiv CH$).

Hydrogen

Diatomic hydrogen ($H-H$) with a $pK_a$ of $35$ and a conjugate base of hydride ($H^-$).

Ammonia (as an acid)

Ammonia ($H-NH_2$) functioning as an acid with a $pK_a$ of $38$ and a conjugate base of amide ($^-\!NH_2$).

Ethene (sp2)

An alkene ($H-CH=CH_2$) with a $pK_a$ of $44$ and a conjugate base of ethenide ($^-\!CH=CH_2$).

Methane

An alkane ($H-CH_3$) with a $pK_a$ of $50$ and a conjugate base of carbanion ($^-\!CH_3$).

Acid strength trend

Acid strength increases as the $pK_a$ value decreases (lower or negative $pK_a$ corresponds to a stronger acid).

Base strength trend

Base strength increases as the $pK_a$ of the conjugate acid increases (a weaker acid yields a stronger conjugate base).

pK_a Values of Common Acids Chart

A reference table outlining the $pK_a$ values, acid formulas, names, and corresponding conjugate bases for common chemical compounds.