Chem. 1A Midterm 1
Version A
Practice Test 2
Name__________________________________________
Student Number _________________________________
All work must be shown on the exam for partial credit. Points will be taken off for
incorrect or no units. Calculators are allowed. Cell phones may not be used for
calculators. On short answer problems you must show your work in order to receive
credit for the problem. If your cell phone goes off during the exam you will have your
exam removed from you.
Fundamentals
(of 24 possible)
Problem 1
(of 8 possible)
Problem 2
(of 16 possible)
Problem 3
(of 16 possible)
Problem 4
(of 12 possible)
Multiple Choice
(of 24 possible)
Midterm Total
(of 100 possible)
1
Fundamental Questions
Each of these fundamental chemistry questions is worth 3 points. You must show work
to get credit, if applicable. Little to no partial credit will be rewarded. Make sure to
report answers in the correct number of significant figures and indicate the proper units.
1)
3 pts
How many kilograms are in 3251 mg?
2)
3 pts
What ionic compound is formed between a) calcium and bromine and b)
potassium and oxygen?
3)
3 pts
Balance the following equations?
a) __MnO2(s)+ __HCl(aq) __Cl2(aq)+ __MnCl2(aq)+__H2O(l)
b) __BCl3(g)+__H2O(l)__B(OH)3(aq)+__HCl(aq)
4)
3 pts
What are the names of the following elements: Mo, Mg, and Sn?
5)
3 pts
What are the names of the following compounds: a) SF6 and b) AlF3?
6)
3 pts
How many moles of Cu are in 3.20 g?
7)
3 pts
How many protons, neutrons, and electrons does a) neon-22 and
b) 209 Bi 3 have?
8)
3 pts
How many widgets are in 2.3×10-20 moles?
2
Short Answer Questions
Each of the following short answer questions are worth the noted points. Partial credit
will be give. You must show your work to get credit. Make sure to report answers in
the correct number of significant figures and indicate the proper units.
1)
8 pts
2)
2a) 6 pts
An iron bar weighed 664 g. After the bar had been standing in moist air for
a month, exactly one-eighth of the iron turned to rust (Fe2O3). Calculate the
final mass of the iron bar and rust.
A solid compound x contains 63.3% Mn and 36.7% O by mass. When X
is heated, oxygen gas is evolved and a new solid compound Y containing
72.0% Mn and and 28.0% O is formed
Determine the empirical formula of X.
Question 2 Continues on Page 4
3
2b) 6 pts
Determine the empirical formula of Y.
2c) 4 pts
Write a balanced equation for the conversion of X to Y.
3)
DDT, an insecticide harmful to fish, birds, and humans, is produced by the
following reaction:
2C6H5Cl(l) + C2HOCl3(l)  C14H9Cl5(l) + H2O(l)
C6H5Cl chlorobenzene, C2HOCl3 chloral, and C14H9Cl5 DDT
In a government lab, 1142 g of chlorobenzene is reacted with 485 g of
chloral.
What is the mass of DDT formed?
3a) 7 pts
Question 3 Continues on Page 5
4
3b) 1 pts
Which reactant is limiting? Which is in excess?
3c) 4 pts
What mass of the excess reactant is left over?
3d) 4 pts
If the actual yield of DDT is 200.0 g, what is the percent yield?
4)
4a) 4 pts
Convert the following into balanced equations
When gallium metal is heated in oxygen gas, it melts and forms solid
gallium(III) oxide.
4b) 4 pts
When solutions of calcium chloride and sodium phosphate are mixed, solid
calcium phosphate forms and sodium chloride remains in solution.
4c) 4 pts
When crystalline potassium chlorate is heated to just above its melting
point, it reacts to form two different crystalline compounds, potassium
chloride and potassium perchlorate.
5
Multiple Choice Q
Questions
Eaach of the fo
ollowing multiple choicee questions aare worth 4 ppoints. Yourr
an
nswers need
d to be filled
d in on the S
Scantron prrovided. Noote: Your
Sccantrons will not be retu
urned to you,, therefore, ffor your recoords, you maay
want
w to mark your answerrs on this sheeet. On the S
Scantron youu need to filll
in
n your perm number,
n
testt version, annd name. Faiilure to do aany of these
th
hings will ressult in the loss of 1 pointt. Your perm
m number is placed and
bu
ubbled in un
nder the “ID number”. D
Do not skip bboxes or put in a hyphenn.
In
n addition, leeave bubbless blank undeer any unusedd boxes. Thhe version
nu
umber (A) iss bubbled in under the “ttest form.”
1. Compoun
nd X2Y is 60
0% X by maass. Calculatte the percennt Y by masss of the com
mpound
X2Y2.
A) 50%
B) 20%
C) 30%
D) 40%
E) Nonee of the abov
ve.
2. Which of the follow
wing is not th
he correct chhemical form
mula for thee compoundd
named?
A) All of
o the formullas are correect.
B) Fe2O3
irron(III) oxide
C) PBr5
ph
hosphorus pentabromidee
D) CoO
O
co
obalt(II) oxid
de
E) CaSO
O4
caalcium sulfitte
3. For a new
w element, 67.16%
6
is an isotope w
with mass 28 0.8 amu, 2.776% is an issotope
with masss 283.7 amu
u, and 30.08
8% is an isootope with m
mass 284.8 aamu. Calcullate the
average atomic
a
masss of this new
w element.
A) 280.8 amu
B) 282.1 amu
C) 283.1 amu
4 amu
D) 313.4
E) Nonee of the abov
ve.
4.
4 What is the
t correct formula
f
for chromium(V
VI) oxide?
A) CrO3
B) Cr2O3
C) Cr6O
D) CrO6
E) Nonee of the abov
ve.
6
5. Consider the following balanced equation:
A(g) + 5B(g)  3C(g) + 4D(s)
When equal masses of A and B are reacted, which is limiting?
A) If the molar mass of A is less than the molar mass of B, then B must be limiting.
B) More information is needed.
C) If the molar mass of A is greater than the molar mass of B, then A must be
limiting.
D) If the molar mass of A is less than the molar mass of B, then A must be limiting.
E) If the molar mass of A is greater than the molar mass of B, then B must be
limiting.
6. How many of the following chemical formulas are written incorrectly?
ClNa BaBr2 LaF2 ClRb
A) All are written incorrectly.
B) One is written incorrectly.
C) Two are written incorrectly.
D) All are written correctly.
E) Three are written incorrectly.
7