Making a salt sim

What the sim shows

Copper(II) sulfate by the excess-insoluble-solid method. CuO + H₂SO₄ → CuSO₄ + H₂O: 25.0 cm³ of 1.0 mol/dm³ acid is 0.0250 mol, so it can take 1.99 g of CuO (Mr 79.5); the rest stays black and is filtered off. The filtrate is boiled down until the hot solution is saturated, then cooled: copper(II) sulfate dissolves 75.4 g in 100 g of water at 100 °C but only 20.3 g at 20 °C (approximate table values), so most of it comes out as crystals, CuSO₄·5H₂O (Mr 249.5), which take their water of crystallisation with them. What stays dissolved in the cold solution is the loss. Precipitation is the other way round: for an insoluble salt such as barium sulfate (BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl, 25 cm³ of each at 0.50 mol/dm³), the residue is the product and the filtrate is waste. A spatula measure is 0.6 g; the burner gives the liquid 250 W. Not counted: water lost below the boil, solution left on the paper and in the beaker, and what the cold rinse dissolves. The clocks run faster than real time.

• Black: copper(II) oxide
• Blue: copper(II) sulfate, and the flame
• White: barium sulfate

Use it in your lessons

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