CAIE IGCSE Chemistry Diffusion Using Kinetic Particle Theory

Practise describing diffusion as random particle motion down a concentration gradient and explain how higher temperature increases the spreading rate.

Exam points

describe net movement from higher to lower concentration caused by continuous random particle motion
explain a gas or solute spreading through air or water until its particles are evenly distributed
predict quicker diffusion on heating because particles gain kinetic energy and move faster

[Maximum number: 4]

Concentrated ammonia solution gives off ammonia gas. Concentrated hydrochloric acid gives off hydrogen chloride gas. Ammonia, $\mathrm{NH}_{3}$ , and hydrogen chloride, HCl , are both colourless gases. Ammonia reacts with hydrogen chloride to make the white solid ammonium chloride.

Apparatus is set up as shown.

Figure for Question 1.2.1—Diffusion using kinetic particle question 1 — CAIE IGCSE Chemistry

After ten minutes a white solid forms in the tube where the gases meet.

(a)

Name the process by which the ammonia and hydrogen chloride gases move in the tube.

[ 1 ]

(b)

The experiment was repeated at a higher temperature.

Predict how the results of the experiment would be different. Explain your answer.

[ 3 ]

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1.2.1—Diffusion using kinetic particle question 1

Question (a)

Question (b)