q12) Which statement is correct about a reaction for which
equilibrium constant is independent of temperature?
A. The rate constants for the forward and reverse reactions do
not vary with temperature.
B. the activation energies for both forward and reverse
reactions are zero.
C. The enthalpy change is zero.
D. There are equal numbers of moles of reactants and
products.
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q18)
Use of the Data Booklet is relevant to this question.
In the Aromas Red Sands aquifer, the drinking water source for
part of California, there are high levels of soluble, toxic
chromium (VI) compounds.
Which Compound in the aquifer's sands is most likely to be
responsible for the formation of the chromium (VI) compounds from
the sparingly soluble chromium (III)-bearing rocks?
A. Al2O3
B CuO
C Fe2O3
D ZnO
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q31)
Carbon forms double bonds with each of the group VI elements
oxygen, sulphur and selenium. In each case, the double bond is
polar.
In the molecules carbon dioxide (CO2), carbonyl sulphide (COS)
and carbonyl selenide (COSe), the polarities of these couble bonds
do not necessarily cancel.
Overall polarity of molecule.
CO2 -- 0
COS ---0.71
COSe --- 0.73
Which factors could account for these observations?
1. The C=S bond is more polar than the C=Se bond.
2. The C=O bond is more polar than the C=S bond
3. The C=Se bond is more polar than the C=O bond.
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q35.
The followng represents the electronic configuration of both a
Group II cation and a Group VII anion.
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
The radius of the anion is approximately twice that of the
cation.
Which reasons explain the difference in size?
1. The cation has a greater nuclear charge than the anion.
2. There is more electron shielding in the anion than in the
cation.
3. On forming the anion from its atom, the extra electron
repulsion makes the ion much larger.
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Instead of me giving the answers outright, deliberately making
vague comments is more fun. It's better to let the candidates
discuss the answer with each other instead.
Hints for Q12.
Temperature change affects position of equilibrium not
only because of enthalpy, but also entropy.
Hints for Q18.
Only 1 of the 4 options could act as an oxidizing
agent.
Hints for Q31.
Electronegativity increases from left to right, bottom to
top, of the Periodic table.
Hints for Q35.
The two ions are isoelectronic (iso = same).
