re<::tional Reaction Kinetics. 25 Points. Consider the gas phase decomposition reaction
ofthe argon dimer (Ar2) to form sta ndard , monatomíc argon (Ar):
A gas cell containing only the dimer is isolat ed, and tbe reaction is aUowed to begin at time
t = O. The initial concentration of the dimer is [Ar2 ) = [Ar2)o and the rate constant is k
a. Plot the concentration ofthe monomeric product, [Ar), as a function oftime and label
the axes accordingly (note: indicate the intercept at t = oo), given that the reaction is
zeroth order in terms of Ar2 • Give an expression for the slope in al\ regions ofthe
diagram between O < t < oo.
. . . e roduct [Ar) as a function of time and \abe\
b. Plot the concentration of the monomer1 p ' t ' oo) aiven that the reaction is
· d' ate the intercept at = , 0·
the axes accordingly (note: in ic . ' th lope in all regions ofthe
second order in terms o f Arz. Gi' ve a n express1on 1or es
diagram between O :5 t < 00 •
Reaction Equilibria. 25 points. The synthesis ofnickel(ll) chloride (NiCl2(s)) is achieved by
reacting chlorine gas (Cli (g)) with nickel(ll) oxide (NiOcs)) at high temperature, re\easing
oxygen gas (Oz (g)). The standard chang e in Gibbs free energy (at P9 = 1 bar) of this
reaction is -15.4 9 kJ moJ·l at 900 K, wher e the per mole basis refers to the moles of nicke\
chloride. Determine the total pre ssure that would be required in the reactor, in an excess of
NiOcs), to achieve a 95% conversion of the chlorine gas at 900 K.
nate Lake. 15 Points. A gigantlc lake ofmolten calcium carbonate (CaC03 CI))
tly been discover ed underneath western North America (ref: Earth and Planetary
Letters, vol. 463, 1 April 2017, p. 25-35). This lake is in equilibrium with the
undlng rock (quicklime, CaOc,)) along with a high-pressure (supercritical) phase
contalning carbon dioxide (C02).
a How man y thermodynamic degrees of freedom are available to this closed underground
b. Hypothetically, a scientist claims to have discovered that the surrounding rock a\so
contains calcite (CaC03 (s)) in equilibrium with the reservoir described above. Can this
be possible? Explain.
c. Hypothetically, a scie ntist claims to have discovered that the surrounding rock contains
calcite (CaCQ3 <•>a)n d that the pressure of carbon dioxide in the headspace above the
lake is occasionally fluctu ating as a function of natural temperature shifts in the Earth.
Can this be possible? Explain.
4. Phase Diagram. 10 points. Draw a simple P-T phase diagram for a common fluid (whose
liquid is Iess dense than its solid) andan un usual fluid (whose Jiquid is denser than its
solid) and label the solid, liquid, gas, and supercritical region , and the critical/triple points.
"Common " "Unusual"
Shenanigans. 25 Polnts. To play a trick on thc new class of studcnts in general
lstry lab, you set out to prep are an organic solu tlon that wlll boll at precisely 100 ºC at
level (to mlmic \Vater). The followlng chemicals are found in the cupboard:
AH/.298 K Sf98K Pu,1.p.313 K
(kJ rnol·1) O K·l mol·1) (bar)
ethanol -276.0 159.9 2.241
pentane -173.5 263.5 2.453
hep tane -224.4 328.6 1.058
octane -250.3 361.2 0.466
a. Choose the two chemica ls that are most likely to forman ideal (Raoultian) solution.
b. De term ine th e comp os ition of the liquid soluti on (from parta) that boils at 100 ºC at
sea le ve !.
c. Determine the composition of the vapor in equilibrium with the solution (from part b ).
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