Chem 150: Problem set 1
1. The following figures represent: (a) a pure element; (b) a mixture of two elements; (c) a pure
compound; (d) a mixture of an element and a compound. Which is which? (Note that there may
be more than one right answer to some parts of the question.)
2. Does the following diagram represent a chemical or a physical change? How do you know?
3. Define the following forms of matter as element, compound or mixture. If you indicate mixture
specify if homogeneous or heterogeneous:
a) Sand
b) Diamond
c) Gasoline
d) Sugar
4. Indicate which of the following changes is a chemical change and which is a physical change:
a) Burning candle wax
b) Melting candle wax
c) Cutting wire
d) Painting your bike
5. Fill in the empty spaces:
Symbol
27
Al3+
_____
150
# of protons
_____
42
_____
# of neutrons
_____
54
_____
# of electrons
_____
_____
_____
Charge
_____
0
_____
Sm
6. Which atomic property is described by the following equation?
Cl
+
e-
→
Cl-
+
energy
7. Name 3 metals, 3 non-metals and 2 metalloids. Name three properties that characterize metals
and three properties that characterize non-metals.
8. Balance the following equations:
C2H6O2 + O2 →CO2 + H2O
P4 + O2 → P4O10
Ca(OH)2 + HCl → CaCl2 + H2O
Fe3O4 + H2 → Fe + H2O
9. In a typical car battery lead (IV) oxide reacts with lead according to the following equation:
(During charging the battery the reverse reaction occurs!)
PbO2
+
Pb
+
2H2SO4
→
2PbSO4
+
2H2O
One way to check whether a battery is still in good condition is to measure the density of the
acid. A good approximation is to assume that battery acid consists only of sulfuric acid and
water. Calculate the amount of lead sulfate that would be formed and the amount of lead that
reacted if the density of the acid changed from 1.2769 g/ml in the freshly-charged battery to
1.1243 g/ml. Assume that there is a total of 3 L of battery acid and that the volume does not
change significantly during the reaction. You’ll need to use a table of densities of aqueous
sulfuric acid to solve the problem.
10. Copper can be deposited from copper salt solutions, such as copper chloride, by reaction with
iron according to the following equation
CuCl2
+
Fe
→
Cu
+
FeCl2
What is the %yield of copper if 150 g Copper chloride reacted and 55 g Copper was obtained?
11. A key component of Portland cement contains the elements calcium, silicon and oxygen.
Analysis shows that the compound contains 34.50 % Ca and 24.18 % Si by weight. Calculate the
empirical formula of the compound.
12. You have to determine the identity of a polymer used to insulate a copper wire in an older
industrial complex. Elemental analysis of the polymer showed that it contained 38.42 % C and
4.88 % H by weight. Which of the following polymers is most likely to be the material in
question?
H
H
C
C
Polyethylene (PE)
H
H
n
H
H
N
C
O
H
C
C
H
Polyurethane (PU)
C
C
O
C
H
C
C
N
H
H
H
O
C
O
C
H
H
n
Cl
H
C
C
Polyvinylchloride (PVC)
H
H
n
13. How much of a 5 M stock solution of NaCl do you need to make 2 L of a 2 M NaCl solution?
14. Name the following ions:
SO42ClPO43CO32ClO3NO3-
15. Write names and formula of the parent acid for the ions above.
End of problem set