Acidic, basic and amphoteric oxides sim
Test ten oxides with water and universal indicator, dilute acid and aqueous alkali, record what you see, and sort each into basic, acidic, amphoteric or neutral.
Acids, bases, salts and ammonia · covers the O-Level, IGCSE topic
What the sim shows
Each test uses 2 cm³ of liquid in a clean test tube: distilled water with 3 drops of universal indicator, dilute hydrochloric acid (2.0 mol/dm³) or aqueous sodium hydroxide (2.0 mol/dm³). Solids go in as one small spatula-tip (about 0.05 g) and are warmed gently in a Bunsen flame; the clamp tilts the tube so its mouth points away from people. Gases are bubbled through at room temperature (each bubbling is about 48 cm³ of gas), and every gas test is done inside the fume cupboard (sulfur dioxide is toxic). Wear eye protection: the alkali is corrosive. Sodium oxide reacts vigorously with water, so it is shown as a teacher demonstration card; carbon monoxide is toxic and is not used in school labs, so its results come from a data card. Water alone sorts only the oxides that dissolve. Insoluble oxides (CuO, ZnO, Al₂O₃) leave the indicator green, so the acid and alkali tests decide: basic oxides react only with acid, acidic oxides only with alkali, amphoteric oxides with both and neutral oxides with neither. The pH comes from a charge balance and is read from the chart to the nearest whole number, so it is approximate: CaO about 12.3 (saturated calcium hydroxide, from its Ksp), Na₂O about 14, MgO about 10 (only slightly soluble), CO₂ about 4–5, SO₂ about 2–3, water 7. In the alkali every bubble is absorbed (the bubbles shrink), and each bubbling is one stage, the same every time: the first makes sodium sulfite (blue, about pH 10.5) or sodium carbonate (violet, about pH 12), the second the hydrogensulfite (yellow, about pH 4.5) or hydrogencarbonate (green-blue, about pH 8.3), and both gases stop there (a third bubbling only nudges SO₂ to orange-yellow, about pH 4, as a little more gas dissolves). Gas results are read straight from the chart, so each stage is recorded the same every time. SO₂ ends more acidic than CO₂ only because sulfurous acid is the stronger acid. The sulfite and carbonate equations shown are the first stage (the model ignores that 2 mol/dm³ sodium hydrogencarbonate would start to crystallise). Copper(II) chloride in the leftover acid looks blue-green. Aluminium oxide reacts slowly and needs 2–3 warmings here (strongly heated, fused alumina hardly reacts at all). The zincate and aluminate equations are in the Singapore form (Na₂ZnO₂, NaAlO₂); IGCSE may write Na₂Zn(OH)₄ and NaAl(OH)₄. Time is shown in steps: each press or drag is one action, and each reaction is shortened to about 2 s. Activities, heat lost while warming and the 0.15 cm³ of indicator are ignored.
- Test tube: 2 cm³ of water + indicator, dilute HCl or NaOH(aq)
- Universal indicator: red (acid) · green (pH 7) · purple (alkali)
- Grid cells fill only when you press Record
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