Suggested Stage 2 Chemistry 2008 SACE Board of SA Exam ...

© SASTA 2009 2008 Exam Solutions 211
Question 8 Comments
(a)
(b) (i)
(ii) (1) [Any two of:]
• Enzyme chain gains energy.
• Hydrogen bonds/ion-dipole and dispersion forces are
overcome.
• The 3-D shape of the enzyme will change.
Must mention:
• If the structure of the enzyme changes then it is unable to
carry out its biological function.
(ii) (2)(A) CO2 + H2O → H2CO3
(B)
CO2 + H2O H2CO3
Acidic or
low pH
(c) (ii) (1) 0.21 – 0.23
(ii)
(2) ppb = µg/L
no. µg Cd = 3.5 x 0.010
(3) ppb = µg/kg
= 0.035 µg
= = 0.035/0.00045 = 77.7777
= 78 ppb (2 sf)
[Any two of:]
• Cd lamp is used
• wavelength used is absorbed only by Cd
• Na absorbs a different wavelength/does not absorb this
wavelength
Note:
Take care when drawing
or copying structures.
Be careful with the
positioning of the bonds.
Note:
Section of molecule
therefore open at least
one end or both.
Note:
Must have three distinct
clear points for full
marks.
Note:
1 mark for correct
species
1 mark for balancing
Note:
Should show full
working for calculations.
Note:
Should show full
working for calculations.
Note:
Must have two distinct
clear points for full
marks.
(iii) Has non zero absorbance for zero concentration of cadmium. Note:
Not does not start at zero