In 1775, the French chemist A L de Lavoisier, father of modern chemistry, showed by an experiment th — Physical Chemistry Chemistry Question
Lavoisier’s experiment
In 1775, the French chemist A L de Lavoisier, father of modern chemistry, showed by an experiment that oxygen is one of the constituents of air.
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...has larger structural defects than the red form. The red mercury oxide can be obtained by a slow pyrolysis of Hg(NO3)2, while the yellow oxide can be obtained by precipitation of aqueous mercury (II) ions in an alkaline medium.
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Model Answer
Correct statement: 100 J K−1 mol‒1
Since Hg2O is a solid, its Sm° should be smaller than that of gases like O2 (200 J K-1 mol-1). In addition, the standard molar entropy of a compound can be 0 J K−1 mol−1
Write down equations for the formation of HgO(s) and Hg2O(s).
Model Answer
HgO formation: Hg(l) + 1/2 O2(g) = HgO(s)
Hg2O formation: 2 Hg(l) + 1/2 O2(g) = Hg2O(s)
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Model Answer
ΔrS° = S°m(HgO(s)) – S°m(Hg(l)) – 1/2 S°m(O2(g)) = ‒105 J K‒1 mol‒1
ΔrG° = ΔrH° ‒ 298 × ΔrS° = ‒55.7×10³ J mol‒1
K° = 5.83×109
c) Hg2O
Calculation:
ΔrH° = ΔfH°(Hg2O(s)) = ‒90 kJ mol‒1
ΔrS° = S°m(Hg2O(s)) – 2 × S°m(Hg(l)) – 1/2 S°m(O2(g)) = ‒150 J K‒1 mol‒1
ΔrG° = ΔrH° ‒ 298 × ΔrS° = ‒45.3×10³ J mol‒1
K° = 8.72×107
Write the chemical equations of these processes.
Model Answer
HgO (red): Hg(NO3)2(s) = HgO(s) + 2 NO2(g) + O2(g)
HgO (yellow): Hg2+(aq) + 2 HO‒(aq) = HgO(s) + H2O(l)
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Model Answer
n(Hg,i) = 122 / 200.6 = 6.08×10‒1 mol
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Model Answer
M(HgO) = 200.6 + 16.0 = 216.6 g mol‒1
m(HgO) = n(HgO) × M(HgO) = 2.8 g
Lavoisier’s experiment is similar to pyrolysis because of the use of heating and the...
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Lavoisier measured volumes at T < 25 °C.
Mercury rust also contains nitride HgxNy.
Model Answer
Correct statement: The yield is not maximum.
Relative difference: (2.8 ‒ 2.3) / 2.8 = 18%, which is a rather high discrepancy. Lavoisier did not reach the maximum yield (maybe for kinetic reasons?). The other statements are not satisfactory as they would explain an apparent yield higher than expected.