CHEM_100 2012
ASSIGNMENT # 2 Due to October 31
REDOX REACTIONS and THERMOCHEMISTRY
1. For an atom in its
elemental form (Na, O2 etc.): O.N.
=
2. For a monoatomic
ion (i.e., Fe3+): O.N.
=
3. For Group 1A (1)
in all compounds O.N.
=
4. For Group 2A (2)
in all compounds O.N.=
5. For hydrogen in
combination with nonmetals O.N.
=
in combination with
metals O.N.=
6. For
fluorine in all compounds O.N.
=
7. For oxygen in
peroxides O.N.=
in
all other compounds (except with F) O.N.=
8. For group 7A (17)
in combination with metals,
nonmetals (except
with O), and other halogens
lower in the group O.N.=
(a)
NO3- b) NO2- c)
NH3 d)
N2O5 e)NO f)NO2
(g) N2O3 h) S8 i) SO42-
(a) 2Al (s) + 3 H2SO4 (aq) à Al2(SO4)3(aq) + 3 H2 (g)
(b) PbO (s) +
CO(g) à
Pb (s) + CO2 (g)
(c) 2H2 (g) + O2
(g) à 2H2O (g)
(d) 5CO(g) + I2O5 (s) à I2 (s) + 5 CO2 (g)
(e) 2Na (s) + 2H2O (l)
à 2NaOH (aq) + H2 (g)
(a) SO32-(aq) + MnO4-
(aq) à SO42-
(aq) +
Mn2+ (aq) (acidic
solution)
(b) MnO4- (aq)
+ Br- (aq) à MnO2 (s) + BrO3-(aq) (basic solution)
THERMOCHEMISTRY
5. {10} When 1 mole of nitroglycerine decomposes, it causes a violent
explosion and releases 5.72 x103 kJ of heat.
C3H5(NO3 )3 (l) à 3 CO2(g) + 5/2
H2O (g) +1/4O2(g) + 3/2 N2 (g)
(a) {2} Is the
reaction exothermic or endothermic? Write a thermochemical equation (ΔH should
be included).
(b) {3} Draw an enthalpy diagram for it.
(c) {5} How much heat
will be released when 1kg of nitroglycerine decomposes?
(a)
absorbs heat
and does work
(b)
gives off
heat and does work
(c)
absorbs heat
and has work done on it
(d)
gives off
heat and has work done on it
(a) H
(b) E
(c) q
(d) T
(e) P
Hess’s Law
N2 + 2O2
à 2NO2
Using the following data:
2NO à N2 + O2 ΔH = -180 kJ
2NO + O2 à 2NO2 ΔH = -112
kJ
9. {20}. Determine the enthalpy
change for the oxidation of ammonia:
4NH3
(g) + 5 O2 (g) à 4 NO(g)
+ 6 H2O(g) ΔH = ???
from the following data:
N2
(g) + 3 H2 (g) à 2 NH3 (g) ΔH = -99.22 kJ
N2 (g) + O2
(g) à 2 NO (g)
ΔH = +180.5 kJ
2H2 (g) + O2 (g) à 2 H2O (l) ΔH = -571.6 kJ
H2O (g) à H2O (l) ΔH = -44.01 kJ
(hint: watch for physical state of water!}