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Chemicals - Technical Library

# Normality & Molarity Calculator

##### Acid and Base Solution Preparation

Instructions
1. Select an acid or base from the drop down menu.
2. Values for density, formula weight and weight percentage will auto-populate but can be changed to reflect lot-specific Certificate of Analysis values.
3. Enter your desired final volume, concentration and select molar or normal for the solution you want to prepare.
4. Click the calculate button to display instructions detailing how to prepare your solution.
5. Click reset to run another calculation.
Select acid or base:

Density: g/mL

Formula weight: g/mol

Weight percentage: % w/w

Desired final volume: mL

Desired concentration:

The molarity calculator tool provides lab-ready directions describing how to prepare an acid or base solution of specified Molarity (M) or Normality (N) from a concentrated acid or base solution.  To prepare a solution from a solid reagent, please use the Mass Molarity Calculator. To dilute a solution of known molarity, please use the Solution Dilution Calculator.

How is the Molarity of a percentage solution calculated?
Using 70% concentrated Nitric Acid as an example: 70% Nitric Acid means that 100 grams of this acid contains 70 grams of HNO3. The concentration is expressed at 70% wt./wt. or 70 wt. % HNO3. Some chemists and analysts prefer to work in acid concentration units of Molarity (moles/liter). To calculate the Molarity of a 70 wt. % Nitric Acid the number of moles of HNO3 present in 1 liter of acid needs to be calculated. Knowing the density of the acid to be 1.413 g/mL, we can calculate the weight of 1 L of 70% HNO3 to be 1413 grams. Knowing that the solution is 70 wt % would then allow the number of grams of HNO3 to be calculated: (0.700)(1413g) = 989.1 grams HNO3 per liter. Dividing the grams of HNO3 by the molecular weight of HNO3 (63.01 g/mole) gives the number of moles of HNO3 / L or Molarity, which is 15.7 M.

The Molarity Calculator Equation:
The following equation is used for calculating Molarity where the concentration is given in wt %:
[(% x d) / MW] x 10 = Molarity
Where: % = Weight %; d = Density (or specific gravity); MW = Molecular Weight (or Formula Weight).
The above equation can then be used to calculate the Molarity of the 70 wt % Nitric Acid:
[(70 x 1.413) / 63.01] x 10 = 15.7 M

How do I calculate the Normality of an acid or base from its Molarity?
There is a relationship between normality and molarity. Normality can only be calculated when we deal with reactions, because Normality is a function of equivalents. Normality refers to compounds that have multiple chemical functionalities, such as sulfuric acid, H2SO4. A 1 M solution of H2SO4 will contain only one mole of H2SO4 in 1 liter of solution, but if the solution is titrated with a base, it will be shown to contain two moles of acid. This is because a single molecule of H2SO4 contains two acidic protons (H+ Ions). Thus, a 1 M solution of H2SO4 will be 2 N. The 'Normality' of a solution is the 'Molarity' multiplied by the number of equivalents per mole.

Why does the calculator use 56.6% weight percentage instead of 28% for Ammonium Hydroxide?
28% Ammonia (NH3) is equal to approximately 56.6% Ammonium Hydroxide.  The Sigma-Aldrich product listings (ex. Product No. 338818) actually list the % Ammonia and not the % Ammonium Hydroxide.  Our calculator is designed to use the % Ammonium Hydroxide.

Is there a Molarity App?
Yes, and it's free! The Molarity App for iPhone, iPod Touch and iPad is available in iTunes and also for Android in Google Play.  If you try our app, please let us know what you think by giving it a rating or writing a review.