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TGW5:
Nitric acid and calcium carbonate
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Notes
on the ‘Think for yourself’ questions
What tells you there is a chemical reaction?
The calcium carbonate is ‘used
up’. A new substance that is in the gas state is formed.
It does not dissolve in water and bubbles out.
Think of the substances that you know to be in the gas state
at room temperature. Which four could be made using the atoms
that are in the formulae of nitric acid and calcium carbonate?
Hydrogen, oxygen, ammonia and carbon
dioxide.
Which one of these four substances is very soluble in water
and would dissolve rather than bubble out?
Ammonia. (Carbon dioxide is
slightly soluble in water at room temperature. Some would
dissolve, but the solution would soon be saturated and the
rest would bubble out).
When tested, the gas turns limewater milky. Which substance
is it?
Carbon dioxide.
Must there be other new substances in solution? Look at the
formulae and account for the atoms.
Yes: calcium, nitrogen and hydrogen
atoms are still unaccounted for. Also, each carbon atom only
uses two oxygen atoms to make carbon dioxide, so there are
some oxygen atoms not accounted for yet.
How would you know when you had added enough calcium carbonate
to react with all of the nitric acid?
There would be some left over calcium
carbonate which would be visible ( because it does not dissolve).
How could you separate out the left over calcium carbonate?
Filter the mixture: a clear colourless,
solution should drip through the filter paper.
How could you separate out any new substance that was dissolved?
Leave it for the water to evaporate.
(Some substances might evaporate with the water, but it would
be worth a
try).
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Science Enhancement Programme CD-ROM 2005 |
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user
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