Part 2 of 2

Lighter, faster

identify / state

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identify: name or select. state: give a concise answer.

In the ring tube, ammonia (M_r 17) spreads from one end and hydrogen chloride (M_r 36.5) from the other, at the same temperature. Complete each answer.

Fill the gaps

The gas with the lower M_r

Its rate of diffusion, compared with the other gas

The white ring forms nearer the end of which gas?

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Scope and sources

Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.

Diffusion explained with the random movement of particles (1.2.1) and the effect of relative molecular mass on the rate of diffusion of gases (Supplement 1.2.2). The experiment is a virtual version of a teacher demonstration with concentrated ammonia; time is schematic. Graham’s law as an equation is not part of this module.

Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.

Official Cambridge syllabus