Question

Question #87882

Answer 1

The normality is the number of gram equivalents in 1 L of solution.

Explanation:

Equivalent mass

A workable definition of equivalent mass (or equivalent weight) is:

the mass of one reactant in a balanced equation divided by the number of moles of another (this isn't the official definition).

Thus, equivalent mass depends on the reaction involved.

Gram equivalents

For example, in the reaction

`"H"_2"SO"_4 + "2NaOH" → "Na"_2"SO"_4 + "2H"_2"O"`

The equivalent mass of `"H"_2"SO"_4` is its molar mass divided by 2 (the coefficient of `"NaOH"`).

In the reaction

`"H"_2"SO"_4 + "Ba(OH)"_2 → "BaSO"_4 + "2H"_2"O"`

The equivalent mass of `"H"_2"SO"_4` is its molar mass divided by 1 (the coefficient of `"Ba(OH)"_2`).

An equivalent mass of a compound is often called an equivalent (eq) or a gram equivalent (geq).

If we call the number of moles of the other compound the n-factor, we can write

`color(blue)(bar(ul(|color(white)(a/a) "geq" = "molar mass"/"n-factor"color(white)(a/a)|)))" "`

Thus, for titration with `"NaOH"`,

`"1 geq of H"_2"SO"_4 = ("98.08 g H"_2"SO"_4)/2 = "49.04 g H"_2"SO"_4`.

For precipitation `"BaSO"4`,

`"1 geq of H"_2"SO"_4 = ("98.08 g H"_2"SO"_4)/1 = "98.08 g H"_2"SO"_4`.

Normality

Normality is defined as the number of gram equivalents of a compound in 1 L of solution.

`color(blue)(bar(ul(|color(white)(a/a)N = "geq"/"litres"color(white)(a/a)|)))" "`

Thus, a `1 N` solution of sulfuric acid for titration with `"NaOH"` will contain 49.04 g of the acid.

A `1 N` solution of sulfuric acid for precipitation of `"BaSO"_4` will contain 98.08 g of the acid.