GCE 'O' 2009 Science (Chemistry) Paper 5
2 You are
provided with a sample of solid salt, X.
Carry out the following
experiments and carefully record your observations.
The volume given below, unless
referring to drops of solution, are approximate and should be estimated rather
than measured.
(a) Using the
smaller tip of the spatula, transfer two spatula tips (about 0.5 g) of solid X
into a large dry hard-glass boiling tube. Place about 3cm3 of
limewater in a test-tube.
Heat the solid carefully but strongly for several minutes. During
the heating process, withdraw several samples of gas from inside the hard-glass
boiling-tube using a teat pipette. The teat pipette should not touch the
boiling-tube. Each time, bubble the gas from the teat pipette through the
limewater.
(i)
Record your observations.
………………………………………………………………………………………….
(i)
A solid residue, Y, remains in the hard-glass
boiling-tube. Suggest identities for the other products formed in this
decomposition reaction.
Carbon
dioxide gas and water………………………………………………………
………………………………………………………………………………………….
[4]
Allow the hard-glass
boiling-tube to cool completely. While you are waiting, continue with the tests
(b) and (c) below.
(b) Adjust the Bunsen burner to give a blue flame.
Moisten the end of a wooden splint
With water
and dip the moist end of the splint into the sample of solid X. Place this
end of the splint in the Bunsen
burner flame.
Record your
observations.
.
(c)
Using the smaller tip of a
spatula, transfer a small amount of solid X into a test-tube and add to
this about 2cm3 of dilute hydrochloric acid.
Record
your observations.
To the cold hard-glass boiling-tube
from part (a), add about 2cm3 of distilled water. Using a glass
stirring rod, stir the mixture until all the residue has dissolved. Now add
more distilled water until the test-tube is about three-quarters full. Stir the
mixture with the stirring rod. This is solution Y.
(d) Using the solution Y, perform the following
tests and record your observations.
(i)
To about 2cm3 of the solution Y, add
about 2cm3 of barium chloride solution. Then add dilute hydrochloric
acid drop-by-drop until about 2cm3 has been added.
………………………………………………………………………………………….
…………….........................................................................................................
ii) To about 2cm3 of the solution Y,
add about 2cm3 of copper (ll) sulphate solution; shake the test-tube
thoroughly. Then transfer the mixture into a boiling-tube. Heat this
boiling-tube carefully, until the mixture begins to boil. Continue gently
heating the boiling mixture until no further change is seen.
………………………………………………………………………………………….
Observations
on heating
………………………………………………………………………………………….
(iii) To about 2cm3 of the solution Y,
add about 2cm3 of dilute hydrochloric acid.
Observation
………………………………………………………………………………………….
(e)
Suggest the name of the anion present in salt X and the name of the anion present in solution Y.
Anion
present in salt X …Hydrogencarbonate, carbonate…………………………….
Anion
present in solution Y….carbonate…………………………………………………
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