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Elements, Compounds and Mixtures
What is Diffusion?
Diffusion is the random movement of
one liquid or gas through another
from a region of high concentration to a
region of low concentration.
Why is Diffusion of a Gas through Air
Slow?
When two gases mix
together, the fast randomly moving
particles collide, and this
slows down their rate of mixing.
Examples are the diffusion of bromine through
air and
the diffusion of hydrogen
chloride and ammonia
through
air.
The Diffusion of Bromine through
Air.
Bromine is a red-brown
liquid that boils at
58 °C.
Bromine gas is also red-brown and can be seen inside a gas jar.
If bromine
gas is allowed to enter a gas
jar containing a vacuum,
the red-brown colour instantly fills the jar
because there are no air molecules to collide with.
This shows that the bromine
molecules are moving very
fast.
When bromine is added to a gas
jar filled with air,
the red-brown gas is seen to slowly
diffuse through the air.
The many collisions between the
bromine molecules and the air molecules
slow down the rate at which the
red-brown bromine gas fills the
jar.
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