## Acid and Base Solution Preparation

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 HNO_{3}. The concentration is expressed at 70% wt./wt. or 70 wt. % HNO_{3}. 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 HNO_{3} 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% HNO_{3} to be 1413 grams. Knowing that the solution is 70 wt % would then allow the number of grams of HNO_{3} to be calculated: (0.700)(1413g) = 989.1 grams HNO_{3} per liter. Dividing the grams of HNO_{3} by the molecular weight of HNO_{3} (63.01 g/mole) gives the number of moles of HNO_{3} / 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, H_{2}SO_{4}. A 1 M solution of H_{2}SO_{4} will contain one mole of H_{2}SO_{4} 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 H_{2}SO_{4} contains two acidic protons (H+ Ions). Thus, a 1 M solution of H_{2}SO_{4} 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 (NH_{3}) is equal to approximately 56.6% ammonium hydroxide. The Sigma-Aldrich product data (e.g., Product No. 338818) reports the % ammonia and not the % ammonium hydroxide. Our calculator is designed to use the % ammonium hydroxide.

For technical support or to provide feedback about this calculator, please email Technical Service.