09/30/15
CHEM 60 Exam 1
Name: __________________________________
Open-End Questions and Problems
Please read the following. To receive full credit for a question or a problem, in addition to the
correct answer, you must show a neat, complete, and logical method of solution where each
number is labeled with the appropriate unit and the final answer is rounded to the correct
number of significant digits. The correct answer without any work shown will generally get
zero credit! When an explanation is required, it should be brief, but accurate and complete.
There are 9 questions for a total of 50 points. (Exam 1 part with multiple choice questions is
worth 50 points. Both parts combined are 100 points total.
1. (4 points) The box below schematically represents of a sample of matter. Fill the blanks.
The number of atoms in the sample is _______ .
The number of elements (types of atom) in the sample is ______ .
The number of molecules in the sample is _______ .
The number of substances in the sample is _______ .
The number of elements (elementary substances)
in the sample is _______ .
The number of compounds in the sample is _______ .
Is the sample gas, liquid or solid? ________________
Is the sample homogeneous
or heterogeneous? ______________________
2. (9 points) Perform the following conversions. Use your judgment to choose the
appropriate format to record the results of your conversions. The format can be either
decimal notation or scientific notation. (You don’t have to show your work.)
3.9×10–5 kg = ________________ µg
20.0 mm = ________________ dm
1.203×1025 nm2 = _______________ cm2
6.89×1015 fm3 = ________________ pm3
1.00 qt = ________________ mL
1 cm3 (exactly) = ________________ µL
3. (2 points) Below are the fragments of two graduated cylinders: a 50-milliter one (on the
left) and a 10-milliliter one (on the right). A student recorded the volumes of the liquid in
the cylinders. However, he made a few mistakes. Correct his mistakes by crossing the
incorrect result and writing the correct one above.
23.0
3.4mL
1.0mL
4.30mL
4. (7 points) Provide a term or a name that matches each of the word descriptions below.
An isotope whose atom is currently used as a
standard in defining the atomic mass unit.
The average mass of all atoms of a particular
element found in nature.
A collection of atoms each of which has in its
nucleus a specific number of protons (the same for
each atom in the collection).
An electrically neutral group of atoms held together
by chemical bonds acting as the smallest
independent particle of a chemical substance.
A chemical substance that is made of atoms of at
least two different elements.
A characteristic of an atom that indicates the sum of
the numbers of protons and neutrons in its nucleus.
A material that has no definite chemical
composition as opposed to a pure substance.
5. (4 points) Although there is only one naturally occurring isotope of iodine, 127I, the atomic
mass of iodine given in the modern periodic table is 126.90447, but not 127. Explain.
6. (6 points) As an elementary substance oxygen exists in the form of diatomic molecules
(O2). How many different types of molecule can be made of the naturally occurring
isotopes of oxygen? Explain.
What is the mass in amu of the heaviest O2 molecule in nature? How many protons,
electrons, and neutrons does that molecule have?
________ amu
________ protons
________ electrons
________ neutrons
What is the mass in amu of the least abundant O2 molecule in nature? How many protons,
electrons, and neutrons does that have?
________ amu
________ protons
Do all O2 molecules have
the same number of protons? _______
________ electrons
________ neutrons
Do all O2 molecules have
the same number of neutrons? _______
What is the molecular mass of oxygen (the average
mass in amu of all naturally occurring O2 molecules)? __________ amu
7. (6 points) Measure (in centimeters) the length and the width of this sheet of paper.
Length: ____________
Width: ____________
Calculate the area of the sheet. Make sure to label the numbers with appropriate units and
give the correct number of significant digits. Show your calculations in the space below.
Area: ____________
Calculate the perimeter of the sheet. Make sure to label the numbers with appropriate units
and give the correct number of significant digits. Show your calculations in the space
below.
Perimeter: ____________
8. (6 points) How many grams of gold are required to make 1.0 m2 of gold foil with the
thickness 0.05 µm? Show work.
9. (6 points) What is the diameter of a sphere made of one mole of aluminum. [𝑉𝑉𝑠𝑠𝑠𝑠ℎ𝑒𝑒𝑒𝑒𝑒𝑒 =
4
3
𝜋𝜋𝑅𝑅 3 where R is the radius.]