World of Chemistry 101
First Exam
Name ______________________
Your answers should always have the correct units to receive credit.
1. (2 pts) Scientific notation is a way to express very large numbers and very small
numbers. Write the following numbers in scientific notation.
263000000000 __________________
0.0000000000216 ___________________
2. (4 pts) The density of an object is defined as the mass per unit volume. Calculate the
density of a piece metal weighing 12.2356 grams and occupying 2.010 cc. Express your
answer to the correct number significant figures. Show your work to receive credit.
3. (2 pts) Given the composition of argon, Ar, in the atmosphere to be 8500 ppm (parts
per million), express this value in percent. Show your work to receive credit.
4. (4 pts) The velocity of light (to three significant figures) is 186,000 miles/sec. Write
this number in scientific notation. Then calculate the number of miles that light has
travelled in one year. Show your work.
5. (4 pts) The velocity of light is 3.0 x 108 m/sec. What is the velocity in miles per
hour (mph). There are 5280 feet in a mile and 3.28 feet in a meter.
6. (3 pts) The mass number of an atom represents the number of protons and neutrons
in the nucleus. The symbol for plutonium is Pu and the stable isotope for plutonium
can be written as 239Pu.
a. How many protons, neutrons and electrons are found in the plutonium atom
with a mass number of 239.
.
b. How many protons, neutrons and electrons are found in 241Pu.
c. How many protons, neutrons and electrons are found in cation, 241Pu3+ .
7. (6 pts) Give the symbol showing the atomic number and the mass number for the
element that has:
a. 10 protons and 10 neutrons. ____________
b. 26 protons and 29 neutrons _____________
c. 47 protons and 61 neutrons ______________
8. (5 pts) Where are the non-metals located in the periodic table? Name two nonmetals.
Where are the metals located in the periodic table? Name two metals.
9. (6 pts) Grain alcohol (booze), C2H6O, can undergo oxidation by oxygen, O2, to
produce carbon dioxide and water. Write the balanced equation that describes this
reaction.
10. (4pts) Metals tend to ____________ electrons to form _____________
Non metals tend to ____________ electrons to form _____________
11. (6pts) Write down the formula of the ionic compounds formed when each of the
following elements react with each other:
a. Sodium reacts with chlorine. _____________
b. Aluminum reacts with sulfur.
______________
c. Calcium reacts with oxygen. _____________
12. (4 pts) There are four free radicals that play a role in catalyzing ozone depletion
reactions: Cl, NO2, ClO, HO. Draw the best Lewis structure for at least two of
these free radicals .
13. (2 pts) State what characteristic is shared by each of these free radicals that
make them so reactive.
14. (15 pts) Write the Lewis structure for each molecule and name each one.
Formula
Name_______
O2
H2O
CO2
CH4
CCl2F2
15. (4 pts) Draw the Lewis structure for sulfur dioxide, SO2, and ozone, O3, and
include all resonance forms. They both have the same Lewis structure!!
SO2
O3
16. (8 pts) Electromagnetic radiation can be represented as a wave. Draw two
different waves to illustrate the difference in their wavelengths. State how these
two waves compare in wavelengths, in frequency and in forward speed. Be
specific for each wave you draw.
17. (6 pts) List four regions of the electromagnetic radiation spectrum in order of
increasing energy.
1.(lowest) ______________
2. _____________ 3_____________ 4. ______________
18. (2 pts) Not only can electromagnetic radiation be described as a wave but it
can also show particle behavior. What do we call a particle of electromagnetic
radiation? __________________
19. (2 pts) The energy region of the electromagnetic radiation spectrum that can cause
the breaking of a chemical bond is _____________________________
20. (2 pts) The energy region of the electromagnetic radiation spectrum responsible for
global warming is ___________________________
21. (3 pts) Today we can warm foods very quickly using a kitchen item
called _________________________. The region of the electromagnetic radiation
spectrum that is used in this device warms the food by causing the
______________ molecules in the food to _______________.
22. (2 pts) Write down the source of each of the following pollutants that are found in
our atmosphere.
Sulfur dioxide
Carbon monoxide
________________________________
________________________________
23. (4 pts) Determine the mass percent composition of sulfur in sulfur trioxide, SO3.
Show your work to get credit.
24. (5 pts) Offer an explanation why it can be so very hot during the daylight hours in
the desert and yet be very cold at night.
22. (3 pts) Name three compounds that contribute to global warming.