Definitions of Equivalent Weight ( Acid-Base Context )

The weight of a compound that contains __ONE
EQUIVALENT__ of a proton (*for acid*) or __ONE EQUIVALENT__ of an
hydroxide (*for base*).

*Examples*:

**(1)** H_{2}SO_{4}
+ 2OH^{-}= 2H_{2}O + SO_{4}^{2-}

__ Molecular weight__ of sulfuric acid (H

* Theoretical Equivalent weight*
of sulfuric acid (H

* Reasoning*:

98.07 g/mol H_{2}SO_{4} * (1
mole H_{2}SO_{4} / 2 equivalents of H^{+}) = 49.03 g/equivalent
of H^{+}

In this example, the magnitude of the equivalent
weight of sulfuric acid is HALF of that of the molecular weight. This is beacuse
according to the balanced chemical reaction, one mole of sulfuric acid reacts
with TWO equivalents of hydroxide *(i.e. same as saying that there are TWO
equivalents of protons per mole of sulfuric acid).*

**(2) **NH_{4}OH + H^{+} = H_{2}O + NH_{4}^{+}

__ Molecular weight__ of ammonium hydroxide (NH

* Theoretical Equivalent weight *of
ammonium hydroxide (NH

* Reasoning*:

35.00g/mol of NH_{4}OH * (1 mole NH_{4}OH
/ 1 equivalent of OH^{-}) = 35.00 g/equivalent of OH^{-}

In this example, the magnitude of the equivalent
weight of ammonium hydroxide is the same as the molecular weight.This is beacuse
according to the balanced chemical reaction, one mole of ammonium hydroxide
reacts with ONE equivalent of H^{+}.

**(3)** H_{2}SO_{4}
+ OH^{-}= H_{2}O + HSO_{4}^{-}

__ Molecular weight__ of sulfuric acid (H

* Theoretical Equivalent weight*
of sulfuric acid (H

* Reasoning*:

98.07 g/mol H_{2}SO_{4} * (1
mole H_{2}SO_{4} / 1 equivalent of H^{+}) = 98.07g/equivalent
of H^{+}

In this example, the magnitude of the equivalent weight of sulfuric acid is the same as the molecular weight. This is beacuse according to the balanced chemical reaction, one mole of sulfuric acid reacts with ONE equivalent of hydroxide.

** Note:** In a laboratory setting,
one can obtain the

*Once the experimental equivalent weight is known, one can
then compare the theoretical equivalent weight (i.e. one that based only one
the balanced chemical reaction) with the experimental one.*