Download CHEM 115 EXAM #1

Name
CHEM 115 EXAM #1
Practice Fall 2008
Circle the correct answer or fill in the blanks. (numbers 1 - 2, 2.5 points each)
1.
The term used to describe a substance composed of two or more elements combined in a
fixed ratio is:
a. solution
d. compound
2.
b. homogeneous mixture
c. heterogeneous mixture
e. aggregate
What do all isotopes of an element have in common?
a. atomic number
b. atomic mass
d. number of neutrons
c. number of nucleons
e. mass number
Fill in the blank with the appropriate word, phrase, or numerical answer.
(numbers 3 - 7, 2 points for each blank)
3.
Matter commonly is found in three physical states. List the two that would be expected
to have similar densities?
4.
and
.
A mixture that has different regions of composition and properties is known as a
mixture.
5.
A scientist obtains the number 16.7249862 on a calculator. If this number actually has
four (4) significant figures, how should it be written?
6.
Round 0.0034169 to four significant figures and express in scientific notation.
7.
What compound should precipitate is NaCl(aq) is mixed with AgNO3(aq)?
(5 points, 1 point per blank)
8.
Use your periodic table to answer the following (use chemical symbols not names)
a. the element expected to be chemically most similar to oxygen
b. an element that exhibits properties between metals and nonmetals
c. an element that is a transition metal
d. a halogen
e. an alkaline earth metal
2
(8 points)
9.
Write the formula for water and calculate the percent by mass of the elements found in
water. FORMULA
PERCENT by MASS work shown here:
(6 points)
10.
Specify the numbers of protons, neutrons, and electrons found in 56Fe and 56Fe3+.
#n
#p
#e
56Fe
56Fe3+
(8 points)
11.
Calculate the number of moles of 3.01 x 1025 atoms of aluminum (Al)
AND the total mass of those atoms in kilograms.
(5 points)
12.
You are given a mixture of water, sand, and sugar. Discuss how you might separate this
heterogeneous mixture into individual substances.
3
13.
Write the names or formulas as needed. (21 points, 1.5 point each)
a. sodium hypochlorite
b. phosphoric acid
c. copper (II) bromide
d. iron (III) sulfate
e. diphosphorus pentoxide
f. hydrochloric acid
g. ammonia
h. FeI3·6 H2O
i. Ni3(PO4)2
j. CO
k. Fe2O3
l. PCl5
m. H2O
n. HClO4
(12 points, 3 points each)
14. Balance the following reactions:
H3PO4 (aq)
Æ
Na3PO4 (aq)
+
H2O (l)
Pb(NO3)2 (aq) +
KI (aq)
Æ
KNO3(aq)
+
PbI2 (s)
C3H8 (g) +
O2 (g)
Æ
CO2 (g)
+
H2O (g)
(a)
NaOH (aq)
(b)
(c)
+
4
(d)
(18 points)
15.
Fe (s)
CH4 (g) +
+
Cl2 (aq)
O2 (g) →
Æ
CO2 (g) +
FeCl3 (s)
H2O (l)
a. balance the above reaction properly and write in the following space:
b. If 30.0 g of CH4 reacts with 128.0 g of O2, how much H2O (in grams) can be formed?
c. If the actual yield is 66.98 g of H2O, then what is the percentage yield?
5
BONUS !!!!!! (for up to 5 points complete the following).
Avogadro’s number is huge. To try to understand how big this number really is consider the
following:
A basketball has a diameter of 9.4 inches. The Earth has a surface area of 196,935,000 sq miles.
How many basketballs are required to cover the Earth with a single layer of basketballs?
(note: if your calculator does not have a key for π, try using 22/7)
What amount in mole(s) does the number of basketballs represent?
What mass of aluminum contains a number of aluminum atoms equal to the number of
basketballs found above?
WOW!