By Contributing Writer — Updated Mar 24, 2022
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Sodium carbonate (Na₂CO₃), commonly known as washing soda, is an inorganic salt prized for its versatility in glassmaking, electrochemistry, toothpaste formulation, and household cleaning. To use it effectively, you’ll need to prepare solutions of a defined concentration, either as a mass percentage or in molarity.
The most convenient way to produce sodium carbonate is by thermal decomposition of baking soda (sodium bicarbonate). Heating the powder to temperatures above 80 °C drives the reaction:
2 NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
Each 2 moles of baking soda yield 1 mole of sodium carbonate, releasing carbon dioxide and water vapor. Use clean glassware or an aluminum pan, and allow the material to cool before handling.
Use the formula:
Mass (g) = (Volume (L) × % mass) ÷ (100 – % mass)
For example, to make a 12 % solution in 350 mL of water:
Mass = 350 × 12 ÷ (100 – 12) = 47.73 g
Measure the calculated amount on a calibrated scale.
Pour the water into a beaker, add the sodium carbonate, and stir until fully dissolved.
Multiply the desired molarity by the volume in liters and the molar mass (106 g mol⁻¹):
Mass (g) = Molarity × Volume (L) × 106
For a 0.2 M solution in 300 mL:
Mass = 0.2 × 0.3 × 106 = 6.36 g
Use a precise scale to obtain the calculated mass.
Begin with 20–30 mL less than the final volume, then add the salt.
Use a spoon or gentle swirling to ensure complete dissolution.
Transfer the solution to a graduated cylinder and top up with distilled water to reach the target volume.
While sodium carbonate is generally safe, avoid inhaling dust and wear gloves and eye protection when handling the powder or during thermal decomposition.
For detailed safety data, consult the Chemical Safety Database.
