Q466-02
Two reactions occurring in the manufacture of sulfuric acid are shown below:
reaction 1 S(s) + O2(g)
 SO2(g)  ΔH
= -297 kJ
reaction 2 SO2(g) + ½O2(g)
SO3(g) ΔH
= -92 kJ |
State the name of the term ΔH.
and whether reaction 1 would be accompanied by a decrease or increase in
temperature.
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ΔH
is the standard enthalpy change for the reaction.
Reaction 1 has negative enthalpy
change. Chemical energy is changing to heat energy, the temperature
increases.
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At room temperature sulfur trioxide SO3 is a solid. Deduce
with a reason whether the ΔH
value would be more negative, or less negative, if SO3(s) instead
of SO3(g) were formed in reaction 2.
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| Energy is required to change from a solid state to a gaseous
state. If sulfur(VI) oxide were formed in the solid state
the energy change would be greater, i.e. more negative. |
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Deduce the ΔH
value of this reaction:
| S(s) + 1½O2(g) SO3(g) |
Predict the sign of ΔS
for reaction 2 and explain your choice.
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| In reaction 2 1½ moles
of gas become 1 mole of gas. There is a decrease in the number
of moles of gas, so the entropy goes down, i.e. ΔS
is negative. |
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Study
question 1 Study
question 3 Study
question 4 Study
question 5
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