How to Calculate Normality (Chemistry)

The weight of a solute in grams per liter of solution is referred to as a solution’s normalcy. Another name for it is the corresponding concentration. The symbols N, eq/L, or meq/L (= 0.001 N) are used for concentration units. For instance, 0.1 N HCl might be used to describe the concentration of a hydrochloric acid solution. A gram equivalent weight or equivalent determines a chemical species’ level of reactivity (ion, molecule, etc.). The chemical species’ molecular weight and valence are used to get the equivalent value. The only concentration unit that depends on a response is normality.

Here are some examples of ways to determine a solution’s normalcy.

Key Takeaways

  • The unit of normality for chemical solution concentration is grams of solute equivalent weight per liter of solution. To represent concentration, one must use a known equivalency factor.
  • The only chemical concentration unit dependent on the chemical process under study is normality.
  • Neither is the use of normality applicable for all chemical solutions, nor is it the most often used measure of concentration. You often employ normalcy in scenarios involving acid-base chemistry, redox reactions, or precipitation processes. Molality or molarity are superior unit choices in the majority of other circumstances.

Normality Example #1

Molarity is the best source of information for normalcy. You need to know the number of moles that dissociate ions. Because each mole of sulfuric acid produces 2 moles of H+ ions, a 1 M solution of the acid (H2SO4) is equivalent to 2 N in acid-base processes.

Since 1 mole of sulfuric acid produces 1 mole of sulfate ions, 1 M sulfuric acid is equivalent to 1 N for sulfate precipitation.

Normality Example #2

1 N (one standard) solution of hydrochloric acid (HCl) is 36.5 grams of HCl.

One gram of a solute’s equivalent per liter of solution is typical. As a powerful acid that fully dissociates in water, hydrochloric acid (HCl) in a 1 N solution would also be 1 N for H+ or Cl- ions in acid-base interactions.

Normality Example #3

Find the normality of a 250 mL solution containing 0.321 g of sodium carbonate.

You must be familiar with the sodium carbonate formula to address this issue. The issue is straightforward if you learn there are two sodium ions for every carbonate ion:

N = 0.321 g Na2CO3 x (1 mol/105.99 g) x (2 eq/1 mol)

N = 0.1886 eq/0.2500 L

N = 0.0755 N

Normality Example #4

If 20.07 mL of 0.1100 N base is needed to neutralize 0.721 g of a sample, calculate the percent acid (equal weight 173.8).

It comes down to canceling out units to get the end outcome. Remember to convert a figure supplied in milliliters (mL) to liters (L). Realizing that the acid and base equivalency factors will be in a 1:1 ratio is the sole “tricky” idea.

When to Use Normality

There are several situations when using normality instead of molarity or another chemical solution unit of concentration is advantageous.

In acid-base chemistry, the term “normality” is used to define the concentration of hydronium (H3O+) and hydroxide (OH-). 1/feq is an integer in this case.

In precipitation reactions, the number of ions that would precipitate is determined by the equivalency factor or normalcy. This time, 1/feq is an integer number.

The equivalency factor in redox processes tells us how many electrons an oxidizing or reducing substance can provide or take. 1/feq may represent a fraction in redox processes.

Considerations Using Normality

In certain circumstances, normalcy is not a helpful unit of attention. It first needs an established equivalency factor. Second, the normalcy of a chemical solution does not have a fixed value. Depending on the chemical process under study, its value may alter. For instance, a solution of CaCl2 with a chloride (Cl-) ion concentration of 2 N would only have a magnesium (Mg2+) ion concentration of 1 N.

Choose your Reaction!