To get the best deal on Tutoring, call 1-855-666-7440 (Toll Free)
Top

Normality

Normality is similar to molarity, but rather than a measure of the number of moles per liter it measures equivalents per liter. For acids and bases, an equivalent can be considered the mass that produces 1 mole of hydrogen or hydroxide ions respectively. 

Normality could be defined as the number of gram equivalents of a solute present per litre (dm3) of the solution at any given temperature and It is expressed as N.The Normality of the solution can also be expressed in terms of mass and equivalent mass 

Normality = $\frac{Equivalents\ of\ solute}{liters\ of\ solution}$The Normality of the solution can also be expressed in terms of mass and equivalent mass
Normality = $\frac{Mass\ of\ the\ solute}{Equivalent\ mass \ of\ the\ solute(E)\ X\ Volume\ of\ the\ solution\ in\ litres(V)}$

In terms of weight, normality of the substance can be expressed as

Normality = $\frac{Wg}{Eg\ /equiv\ X\ V\ litre}$ = $\frac{W\ equiv\ /L}{W\ X\ V}$


Measurements in normality can change with the change in temperature because solutions expand or contract accordingly. Equivalent mass of a substance is the amount of H+ ion or electron supplied or accepted by it or released into a reaction by it.

For example, hydrochloric acid, HCl, can give away its one H+ ion, when reacting with another substance. Thus, equivalent mass of HCl is 36.5/1 = 36.5. This is not so for phosphoric acid. It has a formula of H3PO3. It has 3 replaceable hydrogen atom. So, it has an equivalent mass of: 98g/mol / 3 = 32.67.

Related Calculators
Normality Calculations Area under Normal Curve Calculator
Cumulative Normal Distribution Calculator
 

Normality Definition

Back to Top
A solution is generally described as a homogenous mixture in which some quality of solute (for example NaCl) is dissolved or stabilized, by a solvent (for example H2O). A few ways in which solution composition can be described are as follows.
  1. Molarity
  2. Normality
  3. Molality
  4. Mole fraction
All these concentration terms can be interchanged to another. Depending upon the availability of terms for calculation, we can use the concentration terms, as per our requirement.

Normal Concentration

Back to Top
A solution is best described as normal solution or normal concentration when we know the equivalents of solute added to a known volume.

Example

If 40 grams of NaOH with an equivalent weight or mass of 40 is dissolved in one liter of a solution, normality of the solution is one and the solution is called as ONE

Normal solution

A solution containing 4.0 grams of NaOH is 1/10 N or 0.1 normal or also called as deci normal solution. If the normality of the solution is 0.01, (1/100N), it is called as centi normal solution. On the other hand, if it is 0.001 (1/1000N), this solution will be milli normal solution.

Normal Saline Concentration

Saline solution is a medicinal solution and contains sodium chloride in its aqueous solution. Saline solution contains 9 grams of sodium chloride in 1000 ml or one liter of water.
Since,

Normality = $\frac{equivalents\ of\ solute}{one\ liter\ of\ solution}$

or,

Normality = $\frac{mass\ of\ the\ solute}{equivalent\ mass\ of\ solute\ +\ volume\ in\ liters}$

= 9 / 58.44 + 1 L
= 0.15 N

Therefore, Normality of saline solution is 0.15 N.

Normality of Sulfuric Acid

Back to Top
Concentrated sulfuric acid solutions which come in sealed bottles usually contains one normal solution of sulfuric acid. The concentration of the given solution is written on its labels.

If, say for example, we have 1000cc of sulfuric acid. We need to find its concentration in normality. We can try out the following steps.

Molecular weight of sulfuric acid is 98.07 g/mol
Density of sulfuric acid is 1.87 grams / cc

Density = mass / volume
1.87 g/cc = mass / 1000 cc
Mass of sulfuric acid = 1870 grams.

We have the mass. We know that the equivalent weight of sulfuric acid is molecular mass / 2, because it gives away 2 H+ ions.

Equivalent mass = 98.07 / 2 = 49
So, Normality = 1870 g / 49 + 1L = 37.4N

So, according to this, normality of concentrated sulfuric acid is 37.4N. For laboratory usage, sulfuric acid of 1N normality is used.

Since normality is 1 gram equivalent per liter, its 1N solution would be 49 grams in 1 liter.

Normality of Hydrochloric Acid

Back to Top
Hydrochloric acid is a very widely used laboratory chemical and a strong acid. The solution that comes in bottles to be used in the laboratory is usually IN or uni normal solution.

To calculate the normality of very concentrated solution of 1000cc of HCl (1 liter)
Density of HCl = 1.18 g/cc

Equivalent mass of HCl = molar mass, since it donates only one H+ ion in its solution.
Equivalent mass = 36.5 g/mole.

Mass of 1000cc of HCl = density x volume in cc
= 1.18 g/cc x 1000cc = 1180 grams.

Normality =

$\frac{Mass\ of\ the\ solute\ 1180 grams}{Equivalent\ weight\ of\ acetic\ acid + Volume\ in\ liters\ 36.5 + 1L}$

= 31.46 = 31.5 N

Thus, normality of very concentrated hydrochloric acid is 31.5N.
  Since normality is 1 gram equivalent per liter, its 1N solution would be 36.5 grams in 1 liter.

Molarity to Normality

Back to Top
Molarity and normality terms are very widely used concentration terms. They both find their use in all types of titration of solutions. They are easily inter convertible.

Normality test


Normality is generally used in the case of titration experiments. Usually, two solutions are taken, an acid and a base, in case of an acid- base titration.

A solution should be of known normality or concentration. The below formula is used to calculate the normality of the unknown solution, if the volume and the concentration of the other solutions are known.

V1 X N1 = V2 X N2

Normality test is done to determine the concentration of an unknown solution.

Solved Examples

Question 1: Calculate the molarity of 0.650 N HCl.
Solution:
Normality of HCl = 0.650N. 
So, it has 0.650 equivalents of HCl in 1000ml of solution.
Since HCl releases only 1 proton or H+ ion in its solution, its equivalents is equal to moles.
So, 0.650 equivalents = 0.650 moles in 1000cc or 1000ml.
Thus, Molarity = 0.650M.


Question 2: What will be the normality of 3 molar solution of calcium hydroxide?
Solution:
 
Molarity of calcium hydroxide = 3 M.
Since calcium hydroxide releases 2 electrons in its solution, 1 mole would be equal to 1/2 equivalent.

So, its normality would be: $\frac{3}{2}$ = 1.5 normal.

So, the solution of 3M calcium hydroxide would be 1.5N.
 

Related Topics
Chemistry Help Chemistry Tutor
*AP and SAT are registered trademarks of the College Board.