How to Calculate Concentration in a Tank
- 1). Determine the chemical formula for the substance whose concentration you want to calculate. If your substance is sodium chloride, for example, its formula is NaCl.
- 2). Enter the formula in a molecular weight calculator (see the Resources section at the bottom of this article to access a molecular weight calculator). The molecular weight of sodium chloride, for example, is 58.443 grams per mole.
- 3). Divide the mass of the solute in the tank by the molecular weight you found using the calculator. This gives you the number of moles present in the tank. If 50 kilograms (50,000 grams) of salt were present in the tank, for example, you will have 50,000 / 58.443, which equals 855.5 moles.
- 4). Divide the number of moles in the tank by the total volume of solution the tank contained. This will give you the concentration of the solution. If 855.5 moles are present in 1000 liters of solution, for example, the concentration is 855.5 / 1000 = 0.8555 moles per liter.
- 5). Alternatively, if you need to calculate concentration using % weight / volume, simply divide the mass of solute by the volume. 50 kilograms in 1000 liters, for example, gives you 0.05 kilograms per liter.
- 6). Multiply the number of kilograms per liter by 1000 to convert to grams, then divide by 1000 to convert to milliliters. These two operations cancel, so the number of grams per milliliter is the same as the number of kilograms per liter.
- 7). Multiply the number of grams per liter by 100 to get the number of grams in 100 milliliters. In the example, 0.05 grams per milliliter x 100 equals 5 grams per 100 mL or 5%.
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