Study of Compounds · Hydrogen Chloride · Guided Explainer

Fountain Experiment

A narrated walkthrough. We run the experiment twice — first with plain colourless water, which proves only that the gas is enormously soluble; then again with blue litmus, whose turn to red proves the solution is acidic. Two observations, two separate conclusions.

1 / 8 — subtitles only

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● gas molecules ● plain water (colourless) ready

Walkthrough

    Fountain
    the push is 25× more than needed

    Gas in the flask

    HCl dissolves to about 450 volumes of gas per volume of water. Its solution is acidic, so blue litmus turns red.

    Why run it twice?

    A single red fountain shows two things at once, so students routinely credit the colour to the solubility. Running it first in plain water separates them: the colourless fountain proves only that the gas is enormously soluble. Only when blue litmus is used does the red tell you the solution is acidic. Switch to NH₃ to see the two come apart completely — identical fountain, no colour change.