Question

Iron undergoes two solid-solid transitions as it is heated from
298 K to 1800 K. Given delta H^{o} = 0.900 kJ
mol^{-1} at 1184 K for the a - g transition delta
H^{o} = 0.837 kJ mol^{-1} at 1665 K for a g - d
transition, calculate delta S^{o}_{system} for each
change. Comment on the changes in randomness

Answer #1

Delta G = Delta H - TDelta S.

During a phase transition, Delta G = 0, so substituting and rearranging gives:

Delta H = T Delta S

we know Delta H and the temperature, just substitute and solve for Delta S.

Delta S=Delta H / T=0.9/1184= 7.60*10^-4 KJ/K

also Delta S=Delta H / T=0.837/1665= 5.027*10^-4 KJ/K

All we need to know is that entropy change (delta S) is the change in the amount of disorder between reactants and products; entropy is positive which means that the products are more disordered than the reactants.

4. Thermodynamic data for C(graphite) and
C(diamond) at 298 K is given in the table
below.
delta Hfo (kJ/mol)
o (J/mol K
C(graphite)
0.0
5.740
C(diamond)
1.895
2.377
a) Calculate delta Ho and delta So and
delta Go for the transformation of 1 mole of graphite
to diamond at 298 K.
b) Is there a tempature at which this transformation will occur
spontaneously at atmospheric pressure? Justify your answer.
8. Methanol can be made using the Fischer-Tropsch process
according to...

Diamond
a. At 298 K, what is the Gibbs free energy change G for the
following reaction? Cgraphite -> Cdiamond
b. Is the diamond thermodynamically stable relative to graphite
at 298 K?
c. What is the change of Gibbs free energy of diamond when it is
compressed isothermally from 1 atm to 1000 atm at 298 K?
d. Assuming that graphite and diamond are incompressible,
calculate the pressure at which the two exist in equilibrium at 298
K.
e....

1. Given the values of So given below in J/mol K and
the values of ΔHfo given in kJ/mol, calculate
the value of ΔGo in kJ for the combustion of 1 mole of
butane to form carbon dioxide and gaseous water at 298 K.
S (C4H10(g)) = 273
S (O2(g)) = 208
S (CO2(g)) = 214
S (H2O(g)) = 189
ΔHfo (C4H10(g)) =
-123
ΔHfo (CO2(g)) = -394
ΔHfo (H2O(g)) = -223
2. A particular reaction has a ΔHo value...

(i) The element, S (sulfur), undergoes a phase transition from a
rhombic form to a monoclinic form at 95.4°C. If ΔHtransition=0.38
kJ mol-1, calculate ΔStransition under the above conditions. Show
all working. (ii) Monoclinic sulfur is known to melt at 119°C.
Given ΔHfusion=1.23 kJ mol-1, calculate, showing all working,
ΔSfusion. (iii) Given the S occurs as S8 in solid or liquid forms,
convert the values of the enthalpy and entropy of fusion above to
those expected for S8.

The chemical reaction that causes iron to corrode in air is
given by 4Fe(s)+3O2(g)→2Fe2O3(s)
and
ΔrH∘ = −1684 kJ mol−1
ΔrS∘ = −543.7 J K−1 mol−1
a) What is the standard Gibbs energy change for this reaction?
Assume the commonly used standard reference temperature of 298
K.
b) What is the Gibbs energy for this reaction at 3652 K ? Assume
that ΔrH∘ and ΔrS∘ do not change with
temperature.
c) The standard Gibbs energy change, ΔrG∘, applies only
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1.
Calculate the standard free energy change at 500 K for the
following reaction.
Cu(s) +
H2O(g) à CuO(s) +
H2(g)
ΔH˚f
(kJ/mol)
S˚
(J/mol·K)
Cu(s)
0
33.3
H2O(g)
-241.8
188.7
CuO(s)
-155.2
43.5
H2(g)
0
130.6
2. When
solid ammonium nitrate dissolves in water, the resulting solution
becomes cold. Which is true and why?
a. ΔH˚
is positive and ΔS˚ is positive
b. ΔH˚
is positive and ΔS˚...

1. A 74.20 kg piece of copper metal is heated from 21.5°C to
335.1°C. Calculate the heat absorbed (in kJ) by the metal.
2. A sheet of gold weighing 10.9 g and at a temperature of
17.3°C is placed flat on a sheet of iron weighing 23.9 g and at a
temperature of 52.2°C. What is the final temperature of the
combined metals? Assume that no heat is lost to the surroundings.
(Hint: The heat gained by the gold must...

One mole of NH3(g) is reversibly heated from 300 K to 1300 K at
1.00 bar pressure. Calculate q, w, ∆U, ∆H and ∆S.
Data
The molar heat capacity of NH3(g) is given by the equation
Cpm(T) = a0 + a1T + a2T^2 with constants a0 = 24.295, a1 = 0.03990,
−7.814 × 10−6 .
Cpm is in units of J K−1 mol−1 and T is in units of K.
Hints: dq = dH = CpdT and dS = dq/T...

Thermodynamics: Consider the equilibrium reaction A(g) + B(g)
-><- C(g)+D(g). At T=298 K, the standard enthalpies of
formation of the components in the gas phase are -20, -40, -30, and
-10 kJ/mol for A,B,C, and D, respectively. The standard-state
entropies of the components in the gas phase are 30, 50, 50, and 80
J/(mol K), in the same order. The vapor pressure of liquid C at
this temperature is 0.1 bar, while all other components are
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Can you please check my answers and tell me if they are
correct? thanks
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product (Ksp) expression for each of the following slightly soluble
ionic compounds:
(a) PbCl2
PbCl2(s) --> Pb2+(aq) +
2Cl-(aq)
Ksp
= [Pb2+][Cl-]2
(b) Ag2S
Ag2S(s) --> 2Ag+(aq)
+
S2-(aq) Ksp
=[Ag+]2[S2-]
(c) Sr3(PO4)2 Sr3(PO4)2(s)
--> 3Sr2+(aq) +
2PO43-(aq) Ksp
=[Sr2+]3[PO43-]2
(d) SrSO4 SrSO4(s)
--> Sr2+(aq) +
SO42-(aq) Ksp
=[Sr2+][SO42-]
14. Assuming that no equilibria other than dissolution are
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