Exam 5
Ch 19, 20
CHEMISTRY 1B
100 Points
Name______________________________
SHOW YOUR WORK FOR FULL CREDIT!!!!
1. In each pair, circle the one with the higher entropy.
a. Br2(liq)
or
Br2(g)
b. O2(g)
or
O2(aq)
c. Sn(s)
or
Sn(liq)
d. LiCl(aq)
or
LiCl(s)
e. CH3OH(liq)
or
CH3OH(aq)
2. For the reaction: C2H5OH(liq)  C2H5OH(g) Calculate:
a. Hovap
b. Sovap
c. Tob
d. the boiling temperature of the liquid with an external pressure of 5.25 atm.
(5)
(15)
3. For the reaction below, calculate:
(28)
2 H2O(g) + 2 NO(g) + 2 F2(g)  4 HF(g) + N2O4(g)
o
a. S using So's.
b. Go 298 using So's.
c. Ho by two methods.
d. Use physical grounds to explain the sign of the entropy change.
e. Explain how the enthalpy and entropy changes for this reaction relate the spontaneity of this reaction
in the standard state.
f. Calculate the temperature at which this reaction would be in equilibrium in the standard state.
g. Is this reaction spontaneous in the standard state at 25oC?
4. For the reaction: 2 NO(g) + Cl2(g)  2 NOCl(g)
(27)
Calculate:
a. Ho
b. So
c. Go462
d. K462
e. K635
f. the equilibrium pressure for NO, Cl2, and NOCl, if 15.0 atm. of NOCl comes to equilibrium at 462 K.
g. G462, when the pressures of NO, Cl2, and NOCl are 425 torr, 2.75 atm., and 35.0 torr respectively. Is
the reaction spontaneous?
5. For a spontaneous reaction involving Zr+4/Zr and Ga+3/Ga :
(30)
a. write the balanced net-ionic equation.
b. write the cell notation using 1.75 M Zr(NO3)4 and 6.5 x 10-4 M Ga(NO3)3 .
c. What is the sign of the zirconium electrode?
d. Do electrons flow from Zr to Ga or from Ga to Zr?
e. Calculate Eo for the cell.
f. Calculate E for the cell.
g. Calculate K for the cell reaction at 298 K.
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6. Show what happens (to the salt ions) when pure bromine liquid is placed in contact with a 1.0 M
solution of the following : (Use balanced 1/2 reactions to write balanced net ionic equations for the
reactions that occur.)
(16)
a. FeI2
b. SnCl2
c. Cr(NO3)2
7. A battery is proposed using the following reaction:
2 Ga(s) + 3 Cl2(g)  2 Ga+3 + 6 Cl-(aq)
Calculate:
(14)
a. the maximum voltage for the battery in the standard state.
b. the minimum number of kg of gallium needed and the volume of chlorine gas required at 4.75 atm. and
25oC if the battery is to deliver 8.25 amps of current for 745 hours.
8. Calculate Ksp for PbI2 .
Zr | Zr+4 (0.15 M) || I- (0.025 M) | PbI2, Pb
(15)
E = 1.27 V
9. For [Cd(CN)4]-2, Kf = 1.3 x 1017. If 40.0 mL of 0.075 M Cd(NO3)2 is added to 30.0 mL of 0.500M
sodium cyanide, calculate the equilibrium concentrations forCd+2, CN-, and [Cd(CN)4]-2.
(10)
10. Supply the correct name or formula for each compound below and determine the number of moles of
ions per mole of compound in aqueous solution for b and d.
(10)
a. [Fe (en)2 I2]2CO3
b. triammine triaqua cobalt(III) sulfate
c. K4[Ni Br2 Cl2 I2]
d. aluminum tetrabromo platinate(II)
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