Chemistry IGCSE 2011 Flashcards
Which of these is the formula for a molecule of bromine?
Br2
A small amount of liquid bromine is placed in a gas jar containing air.
The jar is then sealed.
After two minutes, a brown gas is seen just above the surface of the liquid.
After two hours, the whole gas jar is full of the brown gas.
Diffusion
A small amount of liquid bromine is placed in a gas jar containing air.
The jar is then sealed.
After two minutes, a brown gas is seen just above the surface of the liquid.
After two hours, the whole gas jar is full of the brown gas.
Explain, using the particle theory, the observations seen in the gas jar
M1 the bromine/liquid evaporates / the particles
escape (from the liquid)
M2 (bromine fills the gas jar because) the
(gas) particles move freely/randomly/constantly
Iron is a metal that has many uses.
One problem with iron is that it can rust when exposed to air.
(a) Name the two substances that must be present in air for iron to rust.
Oxygen
Water
The table lists some separations.
Complete the table by giving the best method for each separation.
You may use each method once, more than once or not at all.
1) to obtain sand from a mixture of sand and water
2) to separate crude oil into its
components
3) to obtain pure water from sea water
4) to obtain ethanol from a mixture of ethanol and water
Filtration
Fractional distillation
Simple distillation
Fractional distillation
When a mixture of ethanol and water is separated, two colourless liquids, A and B,
are obtained.
Liquid A is ethanol containing a small amount of water.
Liquid B is pure water.
(i) Describe a chemical test to show that liquid A contains water
M1 (add to) anhydrous/white copper(II)
sulfate
M2 turns blue
OR
M1 add to cobalt(II) chloride paper /
cobalt chloride paper
M2 turns pink
Describe a physical test to show that liquid B is pure water.
M1 measure/determine/test its boiling point
M2 100 C
OR
M1 measure/determine/test its freezing point
M2 0C
OR
M1 measure/determine/test its density
M2 1g/cm3
