Everyday salts – chlor-alkali, baking soda, bleaching powder, plaster of Paris and water of crystallisation
ChemistryInorganic ChemistryAges 17–18Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Inorganic Chemistry
A process map of everyday salts: the chlor-alkali cell gives NaOH, Cl₂ and H₂; chlorine and slaked lime give bleaching powder; the ammonia–soda (Solvay) process gives NaHCO₃, which heating turns into Na₂CO₃ and recrystallisation into washing soda; gypsum heated at 373 K gives plaster of Paris, which sets again with water. Each salt shows its equation, the pH of its solution and its uses. A virtual lab heats copper(II) sulfate crystals, gypsum and baking soda in a crucible to constant mass to find the water of crystallisation.
Lesson: Everyday salts: production, pH and uses; water of crystallisation
What it shows
Brine is the starting point for many everyday salts. Electrolysis of brine in a membrane cell gives sodium hydroxide, chlorine and hydrogen, and chlorine with slaked lime makes bleaching powder. The Solvay process gives baking soda, which heating turns into sodium carbonate and recrystallisation into washing soda. Gypsum heated to about 373 K becomes plaster of Paris, which sets hard with water. In the virtual lab you heat samples to constant mass and work out the water of crystallisation yourself. The pH values are typical values; the drying rates are illustrative.
How to use
On the Process map, tap a box or choose a Substance to read its equation, pH and uses, then press Test pH to add it to the table. On Heating hydrates, choose the Sample, Hot plate temperature and Mass of sample. Press Heat for 2 min, then Cool and weigh. Repeat until two weighings agree within 0.002 g, then answer the task. For gypsum, press Add water to watch plaster of Paris set.
Parameters you can change
- Screen Process map, Heating hydrates
- Substance on the map Brine, Chlor-alkali cell, Sodium hydroxide, Hydrogen, Chlorine, Bleaching powder, Solvay tower, Baking soda, Soda ash, Washing soda, Gypsum, Plaster of Paris, Set plaster, Hydrated copper(II) sulfate, Anhydrous copper(II) sulfate
- Sample to heat Blue copper(II) sulfate crystals, Gypsum CaSO₄·2H₂O, Baking soda NaHCO₃
- Hot plate temperature 100 °C (373 K), 150 °C (423 K), 250 °C (523 K)
- Mass of sample 1–3 g
- Cool in a desiccator
Questions to explore
- Why does sodium carbonate solution have a higher pH than sodium hydrogencarbonate solution of the same concentration?
- How many moles of water per mole of CuSO₄ do blue copper(II) sulfate crystals lose when heated to constant mass?
- Why is gypsum not heated to 250 °C to make plaster of Paris for casts?
