How To Calculate The Normality Of NaOH

Normality is a common means of measuring concentration of chemical solutions in science. Specifically, normality measures the gram equivalent weight of a solute per liter of total solution. It is sometimes referred to as equivalent concentration, and is most often used for acid-base solutions. Being able to calculate normality is important for safely preparing chemical solutions such as lye (sodium hydroxide, or NaOH), but before you can do that, you need to understand what equivalent weight is. That can be a little bit tricky.

In chemistry, an equivalent refers to the amount of a substance that reacts with one mole of another substance. For the purposes of calculating normality, those substances are typically a solute and a solvent. Calculating equivalent units requires looking up the molar mass of the chemicals being used. From there, you can take the molar mass and divide it by the number of equivalents to determine the equivalent weight. Once you can determine equivalent weights, calculating normality is simple.

To demonstrate how calculating normality works, let's focus on a common chemical solution: sodium hydroxide, or NaOH. This alkaline chemical is most commonly known as lye, and it is used in a wide variety of home goods including cleaning products and food. Being able to calculate the normality of NaOH is important for safe and effective use of the chemical.

Normality (N) is expressed as grams per liter. The basic formula for normality is as follows: N = grams solute / (liters of solution x equivalent weight). First, you need to calculate the equivalent weight of NaOH. Since lye is a base (alkaline), its number of equivalents is equal to its number of hydroxide ions, which is one. To calculate the molar mass of NaOH, you must add up the atomic masses of each of the elements involved: one sodium atom, one oxygen atom, and one hydrogen atom. If you look up the molar masses of each of these elements, you'll find that sodium is 22.989 g/mol, oxygen is 15.999 g/mol, and hydrogen is 1.008 g/mol. Adding these up gives NaOH a molar mass of 39.996 g/mol. The equivalent weight is then 39.996 g/equivalent.

Let's say you make a solution of 12 grams of NaOH dissolved in 1 liter of water. The formula for normality would then be: N = 12 / (1 x 39.996). The normality of this solution is then 0.30003 N.