Nov 15, 2021 Uncategorized

General Chemistry problems Assignment at an Affordable Cost

1) True or False (circle True or False) (22 pts)
a) Exchange reactions are redox reactions. True False

b) Exothermicity is a driving force for spontaneity. True False
c) In a galvanic cell, reduction occurs at the anode. True False
d) The oxidation state of carbon in CO3
2-
is +6. True False

e) The Second Law of Thermodynamics says that the energy of the universe is True False
constant.

f) The cathode is considered the positive electrode. True False
g) If both ΔS and ΔH are negative for a reaction, the reaction is spontaneous at True False
high temperatures.

h) For chemical reactions, ΔG° changes throughout the reaction until equilibrium is True False
reached.
i) Ag2+ is a good reducing agent. True False

j) The change in enthalpy of a reaction is an intensive property. True False
k) A process at constant temperature and pressure is spontaneous in the direction True False
in which the free energy decreases.
l) H2O2(g) is capable of oxidizing Cu+
. True False
m) Diamond has a standard enthalpy of formation of 0 kJ/mol because it True False
only contains the element Carbon.

n) Group III cations are typically precipitated out as sulfides at low pH when doing True False
qualitative analysis.

o) Knowing the entropy of the surroundings allows you to determine if the process True False
is spontaneous.
p) If Cl2/Cland I2/I- were used to make a galvanic cell, I2 would be at the anode. True False
q) The rate of a reaction is irrelevant to spontaneity. True False
r) The change in entropy of the surroundings is related to the change in enthalpy True False
of the system.
s) Entropy changes in the system are primarily determined by heat flow in and out True False
of the surroundings.
3
t) H2S (g) has more positional entropy than does O2 (g). True False
u) Lead metal will dissolve in dichromic acid. True False
v) The equilibrium constant of a reaction is related to the standard free energy True False
change of the system.
All work and all formulas used are required for full credit
Pencil ONLY
Write CLEARLY
Units and Significant figures ALWAYS MATTER
Put answers in scientific notation where applicable
2) Balance the following redox reaction that occurs in basic solution (8pts):
(Make sure to clearly show each ½ reaction balanced)

MnO4

(aq) + S
2-
(aq) MnO2(s) + S(s)
4
3) For the following reaction, use 2 DIFFERENT methods to calculate ΔG° at 25°C (10 pts)
C2H4(g) + 3O2(g) 2CO2(g) + 2 H2O(l)
a) Method I
b) Method II
5
c) What would be the free energy change at 25°C if the partial pressures of the gases in question 3
were all increased to 2.00atm (7pts)
d) What is the equilibrium constant for this reaction at 25°C? (4pts)
e) What is ∆Suniverse at 25°C for this reaction? (4pts)
4) The molar enthalpy of vaporization of ethanol is 39.3 kJ/mol and its boiling point is 78.3°C. What
is the molar entropy of vaporization for ethanol? (7pts)
6
5) Consider the following line notation representing a galvanic cell:
Pt(s) Cu+
(1.0M), Cu2+
(1.0M) H+

(1.0M), MnO4

(1.0M), Mn2+ (1.0M) Pt(s)
a) Sketch this galvanic cell (labeling all important parts) (7 pts)
b) Write the complete balanced equation for the redox reaction that occurs in this cell: (5pts)
7
c) What is the ɛ° for this galvanic cell? (3pts)
d) What is ΔG° for this cell? (3pts)
e) If the actual cell potential is 1.05V, what is the efficiency of the cell? (3pts)
f) What is the equilibrium constant for this reaction at 25ºC? (3pts)
g) What would the cell potential be if the concentration of Cu+ was increased to 4.5M and the H+
concentration was increased to 2.0M at 25°C but all other species were at 1.0M (4pts)
8
6) For a specific reaction, ΔH = -42 kJ and ΔS = -175 J/K. At what temperatures will the reaction
be spontaneous? (4pts)
7) A student was studying the thermodynamics of the dissolving of an unknown solid. The student
determined Ksp of the solid at 3 different temperatures and then determined the ∆G at those three
temperatures. The student then plotted ΔG/T (J/K) vs. 1/T (1/K) and found the best fit line to be:
y = 57764x – 125.3
a) What is ∆H for this process? (3pts)
b) What is ΔS for this process? (3pts

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