Drying a gas sim
A drying agent absorbs water vapour without reacting with the gas itself.
Drying a gas · covers the GCSE, IGCSE, O-Level topic
What the sim shows
A drying agent absorbs water vapour without reacting with the gas itself. A liquid agent, concentrated sulfuric acid, goes in a wash bottle: the gas comes in by the long tube, which dips under the acid, bubbles up through it and leaves by the short tube, which ends above it. Inlet long, outlet short. A solid agent is packed in a U-tube. Concentrated sulfuric acid and fused calcium chloride dry every gas here except ammonia: the acid neutralises it, and calcium chloride takes it up as a complex. Calcium oxide dries ammonia but reacts with every acidic gas. Turned the wrong way round, the gas comes in over the acid and is never dried, and its pressure forces the acid up the long tube and out of the apparatus. The anhydrous copper(II) sulfate at the outlet is this desk's addition, not the lesson's: dried gas leaves it white, and with no drying agent (the U-tube left empty) the wet gas turns it blue; ammonia turns it violet-blue by itself. The colour shows in the top grains, taken as 1.5 mg of CuSO₄ (this desk's estimate), fully blue after 0.85 mg of water, about 195 s of wet gas. The wet gas is taken as saturated with water vapour at 20 °C (2.34 kPa of 101.3 kPa, standard data); concentrated sulfuric acid is 1.84 g/cm³ (standard data). The flow (0.25 cm³/s), the charges and how much each can take are this desk's estimates; the air already in the apparatus is ignored. The clock runs 4 times faster than real time.
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