Chemistry Reference
In-Depth Information
Air and water
●
Additional questions
1
The apparatus shown on p. 174, Figure 11.6, was
used to estimate the proportion of oxygen in the
atmosphere.
A volume of dry air (200 cm
3
) was passed
backwards and forwards over heated copper until
no further change in volume took place. The
apparatus was then allowed to cool down to room
temperature and the final volume reading was then
taken. Some typical results are shown below.
Volume of gas before = 200 cm
3
Volume of gas after = 157 cm
3
During the experiment the copper slowly turned
black.
a
Why was the apparatus allowed to cool back
to room temperature before the final volume
reading was taken?
b
Using the information given above, calculate the
percentage volume reduction which has taken
place.
c
Explain briefly why there is a change in volume.
d
What observation given above supports your
explanation in
c
? Write a balanced chemical
equation for any reaction which has occurred.
e
Give the name of the main residual gas at the
end of the experiment.
f
Would you expect the copper to have increased
or decreased in mass during the experiment?
Explain your answer.
2 a
Oxygen has an atomic number of 8 and mass
number 16. What is the electron structure of the
oxygen atom?
b
How many electrons, neutrons and protons are
there in the oxygen atom?
c
Oxygen molecules are diatomic. Explain the
meaning of this term.
d
Draw a diagram of the oxygen molecule showing
the outer shell of electrons only. What type of
bonding does the molecule contain?
4
Use the words below to complete the following
passage about limestone and its uses.
abundant chlorine nitrates
monitored coolant fertilisers reactions
pure clay solvent essential
Water is ________ for all life on Earth. It is the
most _________ substance on Earth. Water is not
only used for drinking and washing but also:
●
in chemical ________ , for example in the
production of ethanol from ethene
●
as a ________ to dissolve things
●
as a ________ in some chemical processes.
For us to drink it, water must be relatively ______.
To make the water drinkable, any undissolved solids
are removed through filtration beds. Aluminium
sulfate is added to remove small particles of
________ . _________ is added to kill bacteria.
Water is continuously ___________ because there
are certain substances that eventually find their
way into the water supply. For example, artificial
__________ are washed off farmland and this can
cause the water supply to be contaminated with
nitrates. __________ are harmful to babies.
5 a
Explain what is meant by the term 'pollution'
with reference to air and water.
b (i)
Name an air pollutant produced by the
burning of coal.
(ii)
Name a different air pollutant produced by
the combustion of petrol in a car engine.
c
Some of our drinking water is obtained by
purifying river water.
(ii)
Would distillation or filtration produce the
purest water from river water? Give a reason
for your answer.
(ii)
Which process, distillation or filtration, is
actually used to produce drinking water
from river water? Comment on your answer
in comparison to your answer in
c (i)
.
d
Power stations produce warm water. This causes
thermal pollution as this warm water is pumped
into nearby rivers.
(ii)
Why do power stations produce such large
quantities of warm water?
(ii)
What effect does this warm water have on
aquatic life?
3
Explain the following.
a
Air is a mixture of elements and compounds.
b
The percentage of carbon dioxide in the
atmosphere does not significantly vary from
0.04%.
c
Power stations are thought to be a major cause
of acid rain.
