Sodium carbonate is an inorganic salt with the chemical formula Na2CO3. This compound, used in such industrial applications as glass production, as an electrolyte or as a component of toothpastes, also works as a cleaning agent. Prepare sodium carbonate solutions with a certain concentration, commonly expressed either as a mass percentage of the dissolved compound (for example, a 5 percent solution) or in molarity—the number of moles of such a substance per 1 L of the solution.

## Making solutions with a given mass percentage

Calculate the mass of sodium carbonate needed using the following formula: Mass = (volume x mass percentage) / (100 - mass percentage). For example, to make a 12 percent solution using 350 mL of water, use this equation to determine the amount of sodium carbonate to use: Mass = 350 x 12 / (100 - 12) = 47.73 g

Weigh the calculated amount of sodium carbonate on the scale.

Pour water (350 Ll in our example) into the beaker, and add sodium carbonate.

Mix the solution with the spoon or gently swirl the beaker until the salt dissolves completely.

## Making Solutions with a Given Molarity

Multiply molarity by the solution volume (in liters) and the number 106—the molar mass of sodium carbonate—to calculate the mass of sodium carbonate needed. For example, to make 300 mL of 0.2 molar solution, you will need: 0.2 x 0.3 L x 106 = 6.36 g Note that 300 mL = 0.3 L

Weigh the calculated amount of sodium carbonate on the scale.

Pour distilled water—20 to 30 mL less than the final volume—into the beaker, then add sodium carbonate. In our example, start with 270 to 280 mL of water.

Mix the solution with a spoon or gently swirl the beaker until the salt dissolves completely.

Pour the solution into the graduated cylinder and fill to the final volume with distilled water.