Practice problems for Exam 1.
On the exam, you will be given the useful information shown on the last page of this document
as well as a periodic table.
1. Do the following calculations and pay particular attention to units and significant
120. m 23 m
b) 225 L + 0.27 L
2. Uranium is the element with the highest atomic number that is naturally occurring.
There are three naturally-occurring isotopes of uranium whose exact atomic masses and
natural abundances are listed below. Use this information to determine the atomic
mass of uranium. You must show your work to get credit for this question!
Isotope Atomic mass Natural abundance
U 234.0409521 amu 0.0054%
23U 235.0439299 amu 0.7204%
U 238.0507882 amu 99.2742% 3. Determine if each statement below is true or false (circle your answer). If the
statement is false, change the statement to make it true.
TRUE FALSE Milk chocolate is the best.
a) TRUE FALSE Neutral atoms always have the same number of electrons and
b) TRUE FALSE Most of the mass of an atom is located in the nucleus.
c) TRUE FALSE A sulfide anion and an argon (Ar) atom have the same number
d) TRUE FALSE The uncertainty in 3.4567 g is ±0.0010 g.
e) TRUE FALSE 1340 L should be written as 1.34 x 10 L in scientific notation.
4. Gallium (Ga) has a melting point very close to room temperature (29.7646°C).
a) (8 pts) Determine the melting point of gallium in degrees Fahrenheit and in Kelvin.
b) (3 pts) What is the atomic symbol for a gallium atom that has 40 neutrons?
(Hint: The atomic symbol for a helium atom with two neutrons is 2He .)
2 5. Give the names of the following ionic compounds.
CaSO 4 _______________________________
Fe(ClO3 2 _______________________________
6. Give the chemical formulas corresponding to the following names.
Iron(III) nitride __________________
Phosphorus pentachloride __________________
Perchloric acid __________________
Carbon monoxide ___________________
3 7. HFC-134a (C H F ) is a refrigerant commonly used in automobile air conditioners.
2 2 4
a) What is the molar mass of HFC-134a?
b) If I were to charge my car’s air conditioner with 15.0 pounds of HFC-134a, how
many molecules would be added? (1.00 kg = 2.21 lbs)
c) If the solubility of HFC-134a is 0.15 g in 100. g of water, how many liters of water are
needed to dissolve 15.0 pounds of HFC-134a? (d water= 1 g/mL exactly)
4 8. Consider the following compounds and ions and answer the questions below. If more
than one answer is correct for a question, give all correct answers.
Si O 2 O 3 SO 4 CO N2 H2S BF3 Ar NH 4
a) Which of these have more protons than electron__________________________
b) Which of these have 14 protons and 14 electr