Chem E-1ax
Fall 2014
Problem Set 1 Solutions
(30 points total)
1.
Perform the following calculations, using dimensional analysis if appropriate. Please report your answers with
only three or four digits.
a)
(2 pts)
(2.26 × 10–8) × (3.8 × 10–4) = 8.59 × 10–12
6.10 × 103 – 4.12 × 102 =
b)
5.688 × 103 or 5688
(2 pts) A survey is given to 7% of the graduating class. If 15 people were surveyed, how many members of
the graduating class were not surveyed?
Let x = total number of people in class
15 people surveyed
× 100% = 7% of class was surveyed
x people in class
€
Solve for x = 214.2857 people in class
Number of people NOT surveyed =
214.2857 people in class – 15 people surveyed = 199.2857 people NOT surveyed
= 199 people NOT surveyed
c)
(2 pts) Balsa wood is one of the least dense woods. A sample of balsa wood has a density of 0.13 g/cm3
and a mass of 25.2 grams. What is its volume?
1 cm 3
25.2 g ×
= 194 cm3 or 194 mL or 0.194 L
0.13 g
d)
(2 pts) Hydrogen peroxide is sold in the drugstore as a solution in which only 3% of the solution (by mass)
is hydrogen peroxide. The density of this solution is 1.03 g/cm3. What mass of hydrogen peroxide is contained
in 100.0 mL of this solution?
100.0 mL ×
1 cm 3 1.03 g solution 3 g hydrogen peroxide
×
×
1 mL
1 cm 3
100 g solution
= 3.09 g
Chem E-1ax
Fall 2014
2.
Perform the following calculations using dimensional analysis if appropriate. Please report your answers with
only three or four digits.
a)
(2 pts)
What is the weight (in pounds) of 750. grams of flour? (1 kg = 2.2 pounds)
750 g ×
1 kg
2.2 lbs
×
1000 g
1 kg
(2 pts)
How many cubic inches are in a cubic yard? (1 yard = 3 ft ; 1 ft = 12 inches)
b)
3
1.65 lbs
=
 3 ft   12 inchs 
1 yard × 
×

 1 yard   1 ft 
3
3
c)
=
46700 inches3
or
4.67 × 104 inches3
(2 pts) There are 640 acres in 1 square mile. One mile is 5280 feet, one foot is 12 inches, and one inch is
2.54 cm. Calculate the number of square meters in one acre.
2
1 acre ×
2
2
1 mile 2
 5280 feet   12 inches   2.54 cm   1 m 
×
 ×
 ×
 ×

640 acres  1 mile   1 ft   1 inch   100 cm 
2
= 4047 m2
d)
(2 pts) Determine the total number of protons contained in 15 molecules of water.
The molecular formula for water is H2O. Hydrogen has 1 proton and oxygen has 8 protons, so a single water
molecule has 10 protons.
15 water molecules ×
€
10 protons
=
1 water molecule
150 protons
Chem E-1ax
3.
a)
b)
(6 pts)
(4 pts)
Fall 2014
Write the chemical formula for each of the following species.
i) Potassium cyanide
KCN
ii) Ferric sulfide
Fe2S3
iii) Calcium carbonate
CaCO3
iv) Barium phosphate
Ba3(PO4)2
v) Sulfuric acid
H2SO4
vi) Sodium peroxide
Na2O2
Write an acceptable chemical name for each of the following.
i) N2O4
Dinitrogen tetroxide
ii) AgNO2
Silver nitrite
iii) KMnO4
Potassium permanganate
iv) NH3
Ammonia
4.
(4 pts)
Each of the following pairs of elements will react to form an ionic compound. With
the help of a periodic table, predict the compound which would be formed from the reaction of
each pair. Write the empirical formula of the compound and provide the correct chemical name.
Example:
Sodium and sulfur: Na2S, Sodium sulfide
a)
Magnesium and nitrogen
Mg3N2, Magnesium nitride
b)
Lithium and chlorine
LiCl, Lithium chloride
c)
Calcium and fluorine
CaF2, Calcium fluoride
d)
Aluminum and oxygen
Al2O3, Aluminum oxide