Key to In-Class Group Activity #3 (Chem 101, Summer 2006)
1. Classify each of the following bonds as ionic, polar covalent, nonpolar covalent or no
bond.
a) P-Cl
Polar
Covalent
b) K-Br
Ionic
c) H-Cl
Polar
Covalent
d) C-N
Polar
Covalent
e) B-H
Nonpolar
Covalent
f) K-H
Ionic
2. Classify each of the following as an ionic compound or a covalent compound.
a) KCl
b) PCl3
c) CaSO4
d) HCl
e) HNO3
f) Na2HPO3
Ionic
Covalent
Ionic
Covalent
Covalent
Ionic
3. Given that for water: specific heat = 1.00 cal/g ºC, heat of fusion = 80 cal/g and heat
of vaporization = 540 cal/g
a) Calculate the amount of heat released (in kcal) when 1.00 kg of steam cools from
150.0 ºC to 100.0 ºC and then condenses to liquid water (2 steps).
1.00 kg x (1000 g/1 kg) x 50.0 ºC x 1.00 cal/g ºC = 50,000 cal
1.00 kg x (1000 g/1 kg) x 540 cal/g = 540,000 cal
Total heat released = 50,000 cal + 540,000 cal = 590,000 cal = 590 kcal
b) Calculate the amount of heat released (in kcal) when the 1.00 kg of liquid water cools
to 0.0ºC and then freezes (2 steps).
1.00 kg x (1000 g/1 kg) x 100.0ºC x 1.00 cal/g ºC = 100,000 cal
1.00 kg x (1000 g/1 kg) x 80. cal/g = 80,000 cal
Total heat released = 100,000 cal + 80,000 cal = 180,000 cal = 180 kcal
4. Identify the type of interactive force that occurs between molecules in each of the
following substances.
a) KCl
b) NCl3
c) SBr2
Ionic
DipoleDipoleDipoleDipole
d) Cl2
e) HF
f) H2O
Dispersion
H-bonding
H-bonding
5. Determine which of each of the following would have the higher boiling point.
a) NaCl or HCl
b) Br2 or HBr
c) H2O or H2S
d) C2H6 or C8H18
(Ionic vs.
Dipole-dipole)
(Dipole-dipole
vs. Dispersion)
(H-bonding vs.
Dipole-dipole)
(Larger molecule
= higher dispersion)
6. Balance the following chemical equations.
a)
Zn
b) 3CO
c)
+
+
BaCl2
d) 2Al
2HCl
+
+
Fe2O3


Na2SO4
3CuSO4 
ZnCl2
2Fe

+
H2
+
3CO2
BaSO4
+
3Cu +
2NaCl
Al2(SO4)3
7. Classify each of the following reactions as combination, decomposition, single or
double replacement, combustion and/or redox (may be more than one type for each).
a) N2 + 3H2  2NH3
b) BaCl2 + K2CO3  BaCO3 + 2 KCl
Combination
Double Replacement
c) 2H2O2  2H2O + O2 d) CuO + H2  Cu + H2O
Decomposition
Single Replacement, Redox
e) N2 + 2O2  2NO2
Combination, Combustion
8. For each of the following redox reactions, state which element is oxidized and which
element is reduced.
a) 4Al + 3O2  2Al2O3
Al goes from 0 to +3, so Al is oxidized, O goes from 0 to –2, so O is reduced
b) CuO + H2  Cu + H2O
H goes from 0 to +1, so H is oxidized, Cu goes from +2 to 0, so Cu is reduced
c) 2Na + Cl2  2NaCl
Na goes from 0 to +1, so Na is oxidized, Cl goes from 0 to –1, so Cl is reduced
d) CuCl2 + Zn  ZnCl2 + Cu
Zn goes from 0 to +2, so Zn is oxidized, Cu goes from +2 to 0, so Cu is reduced