Conjugate Acids and Conjugate Bases

Key Questions

How can I identify conjugate acids and bases?

Answer:

Here is one answer.

Explanation:

See this Socratic answer.

And here's another way to look at it.

A conjugate acid contains one more H atom and one more + charge than the base that formed it.

A conjugate base contains one less H atom and one more - charge than the acid that formed it.

Let us take the example of bicarbonate ions reacting with water to create carbonic acid and hydronium ions.

HCO₃⁻ + H₂O → H₂CO₃ + OH⁻
base + acid → Conj A + Conj B

We see that HCO₃⁻ becomes H₂CO₃. It has one more H atom and one more + charge (-1 + 1 = 0). So H₂CO₃ is the conjugate acid of HCO₃⁻.

The H₂O becomes OH⁻. It has one less H atom and one more – charge. So OH⁻ is the conjugate base of H₂O.

Ernest Z. · 25 · Jul 3 2014
What factors determine acid strength?

Acid strength is determined by the amount of that acid that actually ionizes. Acids are molecular covalent compounds which you don't expect to ionize (release an $H^{+}$ $H^+$ and leave behind the conjugate base, or $C l^{-}$ $Cl^-$ for example).

The strongest acids ionize 100%. There are 6 that most consider to be the "STRONG" acids: HCl, HI, HBr, HNO_3 $, H_{2} S O_{4}$ $, H_2SO_4$ and HClO_4#. These split apart 100%.

All other acids are weak acids and ionize to a much lesser amount. For example, acetic acid, like most weak acids, ionizes, 5%.

Pat B. · · Apr 14 2014
What are conjugate acid-base pairs?

All acids have a conjugate base. All bases have a conjugate acid. Acids "donate" $H^{+}$ $H^(+)$ when they react. This is most easily seen when they dissociate in water:

$H_{2} S O_{4}$ $H_2SO_4$ + $H_{2} O$ $H_2O$ => $H S O_{4}^{-}$ $HSO_4^-$ + $H_{3} O^{+}$ $H_3O^+$

In this example, sulfuric acid ( $H_{2} S O_{4}$ $H_2SO_4$ ) is an acid because it "donates" $H^{+}$ $H^+$ to the water. It becomes the hydrogen sulfite ion ( $H S O_{4}^{-}$ $HSO_4^-$ ) which is the conjugate base of sulfuric acid.

The same idea applies to a base:

$N H_{3}$ $NH_3$ + $H_{2} O$ $H_2O$ <=> $N H_{4}^{+}$ $NH_4^+$ + $O H^{-}$ $OH^-$

Ammonia ( $N H_{3}$ $NH_3$ ) is a base because is "accepts $H^{+}$ $H^+$ from water to come its conjugate acid, the ammonium ion ( $N H_{4}^{+}$ $NH_4^+$ ).

This video gives an overview of acids and bases; the second half is about conjugate pairs:

Simple, easy to understand can be on this site http://www.chemteam.info/AcidBase/Conjugate-Pairs.html

Matt N. · 3 · Apr 14 2014

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Conjugate Acids and Conjugate Bases

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Acids and Bases