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A comprehensive set of homework problems and solutions covering key concepts in chemical thermodynamics and electrochemistry. It delves into topics such as equilibrium constants, gibbs free energy, standard potentials, and the debye-huckel limiting law. The problems provide practical applications of these principles, enhancing understanding and problem-solving skills in these areas.
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Chem 113A Homework # 6
Solutions
2
3
comes to equilibrium at
a total pressure of 1 atm, analysis of the gas shows that at 700 K and 800 K,
๐
๐๐ป 3
๐
๐ป 2
= 2. 165 and 1. 083 , respectively, if only ๐ป
2
(๐) was initially present in the
gas phase and ๐น๐๐(๐ ) was in excess.
a) Calculate ๐พ
๐
at 700 K and 800 K.
b) Calculate โ๐ป
๐
ยฐ
and โ๐
๐
ยฐ
at 700 K and 800 K (assuming they are both
independent of temperature).
c) Calculate โ๐บ
๐
ยฐ
for this reaction at 298 K.
2 +
2 +
. The concentrations of CuSO 4
and ZnSO 4
are
2.50 and 1.10 ร 10
m, respectively.
a) Calculate E setting the activities of the ionic species equal to their molalities
b) Calculate ๐พ
ยฑ
for each of the halfโcell solutions using the DebyeโHuckel
limiting law.
c) Calculate E using the mean ionic activity coefficients determined in part (b).
2
= 2HI at equilibrium at T= 870 K and p =
1 bar. If ๏Gห (870K, 1 bar) = - 48.96 kJ, determine K, ฮพ and the equilibrium
amounts of H 2
2
and HI (in mol) if the intial composition was nห(H 2
mol, nห(I 2
) = 0.400 mol, and nห(HI) = 0.200 mol.
ln ๐พ
๐
ยฐ
3
J/mol
๐
This equilibrium constant was calculated in the pressure standard state (since we
calculate the equilibrium composition.
๐ฅ
๐
ยฐ
โ๐
๐
ยฐ
Let the extent of reaction at equilibrium be denoted ๐. The number of moles at
equilibrium and the mole fractions for each reactant and product are:
๐ป
2
๐ป 2
ยฐ
๐ผ
2
๐ผ 2
ยฐ
๐ป๐ผ
๐ป๐ผ
ยฐ
๐ป
2
๐ ๐ป
2
๐
3 โ๐
9
๐ผ
2
๐ ๐ผ
2
๐
4 โ๐
9
๐ป๐ผ
๐
๐ป๐ผ
๐
2 + 2 ๐
9
๐ฅ
๐ป๐ผ
2
๐ป
2
๐ผ
2
2
2
2
2
The roots of the equation are ๐ = 0. 411 ๐๐๐ and ๐ = 0. 293 ๐๐๐. Since a value
for the extent of reaction at equilibrium ๐ = 0. 411 ๐๐๐ is unphysical (it leads to
negative moles for H 2
and I 2
at equilibrium), the extent of reaction at equilibrium
is:
Finally, the equilibrium compositions are:
๐ป
2
๐ผ
2
๐ป๐ผ
2
2
Given that, for the production of liquid formaldehyde from the same reactants,
๐
0
๐พ๐ฝ
๐๐๐
at 298 K and that the vapor pressure of formaldehyde is
1500 Torr at that temperature.
mNa
= 0.14 m, mCl
= 0.10 m, mHCO 3
โ = 0.025 m. Calculate the ionic strength
of blood plasma.
2
2
2
2
2
2
At 1000 K, the equilibrium composition of the reaction mixture is
Substance ๐ถ๐
2
2
2
Mole % 27.1 27.1 22.9 22.
Calculate ๐พ
๐
and โ๐บ
๐
ยฐ
at 1000 K.
๐ฅ
๐
ยฐ
) ( 1000 ๐พ) ln( 0. 714 ) = 2. 80 ร 10
3
2 +
2 +
. The concentrations of CuSO 4
and ZnSO 4
are 2.50 and 1.10 ร 1 0
3
m, respectively.
a) Calculate E setting the activities of the ionic species equal to their molalities.
b) Calculate ๐พ
ยฑ
for each of the halfโcell solutions using the DebyeโHuckel
limiting law.
c) Calculate E using the mean ionic activity coefficients determined in part (b).
ยฐ
is independent of T for a
specific reaction. The following data are given at 25ยบC:
a) From Equation 6.64, โซ
๐ ln ๐พ
๐
๐พ ๐
(๐
๐
)
๐พ
๐
(๐
0
)
1
๐
โ๐ป
๐
ยฐ
๐
2
๐
๐
๐
0
๐๐. To a good
approximation we can assume that the heat capacities are independent of
๐
๐
2
ยฐ
โ 4
๐
2
โ 4
c) What value would you obtain if you assume that โ๐ป ๐
ยฐ
is independent of temperature
in the range 298.15 K to 1350 K?
๐
ln ๐พ
๐
๐ 2
โ 3