# Question 87882

Apr 1, 2017

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

$\text{H"_2"SO"_4 + "2NaOH" → "Na"_2"SO"_4 + "2H"_2"O}$

The equivalent mass of ${\text{H"_2"SO}}_{4}$ is its molar mass divided by 2 (the coefficient of $\text{NaOH}$).

In the reaction

$\text{H"_2"SO"_4 + "Ba(OH)"_2 → "BaSO"_4 + "2H"_2"O}$

The equivalent mass of ${\text{H"_2"SO}}_{4}$ is its molar mass divided by 1 (the coefficient of ${\text{Ba(OH)}}_{2}$).

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 $\text{NaOH}$,

${\text{1 geq of H"_2"SO"_4 = ("98.08 g H"_2"SO"_4)/2 = "49.04 g H"_2"SO}}_{4}$.

For precipitation $\text{BaSO} 4$,

${\text{1 geq of H"_2"SO"_4 = ("98.08 g H"_2"SO"_4)/1 = "98.08 g H"_2"SO}}_{4}$.

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 $\text{NaOH}$ will contain 49.04 g of the acid.

A $1 N$ solution of sulfuric acid for precipitation of ${\text{BaSO}}_{4}$ will contain 98.08 g of the acid.