2004 HKCEE CHEMISTRY PAPER 1

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2004 HKCEECHEMISTRY PAPER 1

• Comments

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• a. some candidates wrongly gave CaO as the
  product
• b. (i) - did not read the question carefully
  and failed to draw the beaker.
• - did not show proper collection of gas in
  their
• diagrams
• c. candidates had to mention the different
  observations
• for both metals, but many candidates failed to
  give
• comparisons

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• failed to give the observations for both
  substances under the same chemical test
• b. heating should be required
• c. were not aware that dilute sulphuric acid
  would have no
• reaction with copper.
• (some even thought that sulphur dioxide would
  be evolved)

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• a. did not know what iodine tincture was!
• (They answered that it was made by dissolving
  iodine in
• tincture.)
• b. (i) did not use the word reduction,
  and some wrongly
• thought that the process was due to the
  the dye being
• bleached by sulphite
• (ii) could not make a comparison between the
  two
• processes (i.e. one is a chemical process
  and the
• other one is a physical process)

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4. wrongly mentioned that carbon monoxide or
carbon dioxide could cause acid rain wrote a
lot on the harmful effects of acid rain, which
were not required by this question did not
state the formation of each pollutant
clearly the methods for minimizing the
pollutants were not specific enough (e.g. did not
state which pollutant was reduced) many wrong
methods were suggested (e.g. electrostatic
precipitator to remove NOx, catalytic converter
to remove SO2)
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• could not distinguish between atoms, ions and
  
• molecules
• some wrongly thought that SiO2 was simple
  molecular structure

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• a. (iv) could not deduce the formula of water
  based on the
• volume ratio of hydrogen and oxygen.
• b. (iii) (2) Some candidates wrongly gave the
  ionic half
• equation Fe2 Fe3 e- as the
  answer.
• c. (iv) could not use the correct terminology of
  
• incineration and landfilling.
• answers such as low cost, cause less
  pollution or
• more convenient were too general!

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• a. (i) misunderstood the word meniscus
• They wrote that until the water level
  reaches the
• meniscus of the volumetric flask.
• (iii) forgot that only one-tenth of the total
  amount of acid was used in the titration.
• b. (i) wrongly stated the hydrophilic part as
  Na and
• hydrophobic part as RCOO-.
• (ii) did not realize that sea water was hard
  water
• They focused on the pollution problems
  such as the
• rapid growth of algae.

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• c. (i) (1) wrongly thought that conc. sulphuric
  acid would decompose into sulphur
  dioxide in air
• mixed up the concept between
  dehydration and
• hygroscopic.
• (2) could not state the correct
  observation for the
• condensation reaction.

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• a. (iii) wrongly stated that some carbon dioxide
  was trapped
• inside the apparatus
• b. (i) could not state hydrated iron(III)
  oxide
• (iii) wrong protection methods were given
  (candidates did
• not pay attention to the methods of rust
  prevention in our daily life)
• (v) poor spelling for anodization
• c. (i) failed to explain the colour change in
  terms of the
• concept of reduction or oxidation
• (ii) many wrong answers such as checking the
  alcohol
• content in bloodstream or urine/to walk
  along a
• straight line/measure the redness of the
  face

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• a. (iii) could not describe metallic bond in
  terms of
• electrostatic attraction between metal
  cations and
• delocalized electrons
• (v) - some candidates could not make use
  of the group
• number and atomic number to deduce the
  values
• of x and y
• - failed to give the correct equation for
  the reaction
• between bromine and sodium hydroxide
• c. (ii) could not give the structure of the
  organic compound
• (i.e. weak in tackling unfamiliar
  problems)