In Progress
Lesson 1, Topic 1
In Progress

Diffusion past paper questions

 Nov 2012 Q3 

A small amount of liquid bromine is added to a container which is the sealed

Br2(l)    →  Br2(g)   

Use ideas of the kinetic→ theory to explain why, after about an hour, the bromine molecules have spread uniformly to occupy the whole container


Particles of bromine with a lot of energy leave the liquid bromine and they diffuse and the particles move in all directions



 Nov 2014 Q3 (a),(b), (c) 

(a) Different gases diffuse at different speeds

(i) What is meant by the term diffusion?

(ii) What property of a gas molecule affects the speed at which it diffuses?

(b)Helium is a gas used to fill balloons. It is present in the air in very small quantities. Diffusion can be used to sperate it from the air

Air at 1000°C is on one side of a porous barrier. The air which passes through the barrier has a larger amount of helium in it

(i) Why does the air on the other side of the barrier contain more helium?

(ii) Why is it an advantage to have the air at a high temperature



(i) movement of molecules from region of high concentration to region of low concentration

(ii) molecular mass


(i) because helium atoms are lighter than molecules in air

(ii) because molecules of air move faster at high temperatures


May 2015 Q6 (c) 

Gases diffuse, which means that they move to occupy the total available volume

(i) Explain, using kinetic particle theory, why gases diffuse

(ii) When the colourless gases hydrogen bromide and ethylamine come into contact, a white solid is formed

The following apparatus can be used to compare the rate of diffusion of the two gasses

Predict at which position A, B or C the white solid will form. Explain your choice


(i) Because particles collide with each other and move in randomly in all directions

(ii) C , because ethylamine has a lower molecular mass than HBr so ethyl amine diffuses faster