Chemistry 161. Test Two. March 23, 2010. Name ____________________________________________
You are not allowed to share calculators on this test, nor may you use a cell phone or other communication device for a calculator.
You may borrow a calculator from Dr. Overway if necessary. There is a periodic table available as well as a table of Hf data.
Cp = 75.3 J/mol oC for H2O(l)
Cp = 37.1 J/mol oC for H2O(s)
Hvap = 40.67 kJ/mol for H2O
Part One. Twelve points.
_____ 1) One liter of an 0.345 M solution of sodium phosphate requires ___ g of solute.
a- 24.1 g
b- 40.7 g
c- 56.6 g
d- 65.3 g
_____ 2) 164.33 mL of 0.3527 M potassium bromide is diluted to 450.0 mL. The new solution is
a- 0.1288 M
b- 0.9658 M
c- 0.3527 M
d- 0.2251 M
_____ 3) What is the oxidation number of phosphorus in KPF6?
a- 3+
b- 5+
c- 3d- 0
_____ 4) What is the oxidation number of Cr in Cr2O72-?
a- 6+
b- 12+
c- 7+
d- 3_____ 5) Which of the following reactions is an oxidation?
a- Zn2+ → Zn0
b- SO2 → SO32c- LiNO3 → Li+ + NO31d- 2 Br1- → Br0
_____ 6) 44.62 mL of OH- is used to titrate 25.00 mL of 0.3266 M acid. The concentration of the base is
a- 0.5829 M
b- 0.4366 M
c- 0.1830 M
d- 0.3266 M
_____ 7) How much energy is needed to raise the temperature of 234,6 g of water from 12.5 oC to 87.1 oC?
a- 8.70 kJ
b- 17.7 kJ
c- 1.02 kJ
d- 0.500 kJ
_____ 8) The Hf of Ca(s) is 0 kJ/mol.Hf of Ca(g) is
a- -167.2 kJ/mol
b- +177.8 kJ/mol
c- 0 kJ/mol
Part Two. On ALL problems with numeric answers you must show the setup for your work.
1) (12 points) For each of the following reactions, determine the Hrxn from the enthalpies of formation?
3 NH4NO3 (s)
NaOH (aq)
+
C10H22 (l)
+
14 O2 (g) →
+
H3PO4 (aq)
→
3 N2 (g)
+
H2O (l) +
17 H2O (g)
+
10 CO2 (g)
Na3PO4 (aq)
2) (10 points) For the following reaction, determine the theoretical amount of each product that can be formed from 8.357 g of
NaAu(CN)2.
2 NaAu(CN)2 (aq)
+
Zn(s)
→
2 Au(s) +
Na2(Zn(CN)4) (aq)
3) (10 points) Uranium tetrafluoride is prepared by reacting uranium oxide with HF in the following equation. 12.35 g of UF 4 is
prepared from 21.56 g of UO2. What is the percent yield of the UF4?
UO2 (s)
+
4 HF (aq)
→
UF4(g) +
2 H2O (l)
4) (10 points) A 1.222 g sample of benzene (C6H6) is reacted in a bomb calorimeter with a C = 4.22 kJ/ oC. The temperature change in
the calorimeter is from 21.48 oC to 27.55 oC. What is H for the following reaction?
C6H6 (l)
+
15/2 O2 (g)
→
6 CO2 (g)
+
3 H2O (g)
5) (12 points) Balance each of the following reactions, indicate the proper states, write the ionic and net ionic reactions.
Pb(NO3)2 (
Ba(OH)2 (
)
) +
Na2SO4 (
+
HCl (aq)
) →
→
PbSO4 (
H2O (
)
)
+
NaNO3 (
+
BaCl2 (
)
)
6) (18 points) Definitions in words!
Enthalpy
Exothermic
Internal energy of a system
Thermochemistry
Electrolyte
Oxidation
.
Substance
Ag+ (aq)
NH4NO3 (s)
C10H22 (l)
H2O (g)
CO2 (g)
OH1- (aq)
H3PO4 (aq)
H2O (l)
PO43- (aq)
C3H8 (g)
H2O2 (l)
O (g)
N (g)
NH41+ (aq)
NO31- (aq)
H+ (aq)
Hof (kJ/mol)
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