Practice Exam AP Chemistry Midterm 1st 9 weeks
Section I - Multiple Choice (50%)
Directions: Each set of lettered choices below refers to the numbered statements
immediately following it. Select the one lettered choice that best fits each statement
and then blacken the corresponding space on the Scantron. A choice may be once,
more than once, or not at all in each set. You must choose 40 out of 50, leave 10
blank. Wrong answers have a 0.25 point penalty, so no guessing!
Questions 1-3
A.
B.
C.
D.
E.
phosphorus
beryllium
sodium
magnesium
sulfur
1. Which of the above is a chalcogen?
2. Which of the above has a nonmetal with an oxidation number of +6?
3. Which of the above forms salts that are all soluble in water?
Questions 4-6
A.
B.
C.
D.
-2
CrO4
SO3-2
H+
SO4-2
+2
E. Mn
4. In a reaction between potassium chromate and sodium sulfite in acidified
solution, which of the above will serve as the oxidizing agent?
5. Which of the above is added to the reactants side to denote that the reaction is
occurring in acidic solution?
6. Forms a yellow color in solution
AP Practice Exam
Page 2
Questions 7-10
A.
B.
C.
D.
E.
HNO3
N2O5 + H2O
Zn + CuSO4
Cu + ZnSO4
2NH4Cl + Ca3(PO4)2
(NH4)3PO4 + CaCl2
2C2H2 + 5O2
4CO2 + 2H2O
Pb+2 + 2I-1
PbI2
7. Is an example of a single displacement.
8. Is an example of a combustion reaction
9. Is an example of a precipitation reaction.
10.
Is a example of a metathesis reaction.
11.
The value of the acid-dissociation constant, Ka, for a acetic acid is 2 x 10-5. The
pH of a 0.20M acetic acid solution is closest to?
A. 2-3
12.
D. neutral
E. above 7
synthesis
single displacement
metallic chlorate decomposition
double displacement
combustion
Sodium sulfate reacts with barium chloride to form the insoluble compound:
A.
B.
C.
D.
E.
14.
C. 5-6
Carbon dioxide and water are products of this type of reaction:
A.
B.
C.
D.
E.
13.
B. 4-5
chlorine
water
potassium nitrate
sodium chloride
barium sulfate
Which of the following does NOT behave as an electrolyte when it is dissolved
in water:
A. CH3CH2OH
B. Na2CO3
C. NH4Br
D. CH3COOH
E. HBr
AP Practice Exam
Page 3
15.
Which of the following will NOT decompose into an acid anhydride and water:
A. H2CO3
16.
E. HNO3
B. KX2
C. K3X2
D. K2X3
E. KX
B. 2.0
C. 3.0
D. 4.0
E. 5.0
Which of the following describes a chemical property?
A.
B.
C.
D.
E.
19.
D. H3PO4
Which electro negativity is probable for an alkali metal?
A. 1.0
18.
C. H2SO3
Potassium reacts with an element to form a compound with the general
formula K3X. What would the most likely formula be for the compound formed
between the aluminum and element X?
A. K2X
17.
B. NaHCO3
Sodium chloride crystals are brittle.
Phosphine combines explosively with oxygen.
Copper(II) sulfate forms blue crystals.
Purification of alcohol by distillation.
Mercury is a liquid at room temperature.
For the radioisotope Hydrogen-3, tritium, give the A, Z, protons, neutrons and
electrons in order:
A. 0,2,1,1
B. 1,1,2,2
C. 1,1,2,0
D. 1,2,0,1
E. 2,1,0,1
20.
The geometrical arrangement of atoms in the sulfate ion is
A. Tetrahedral
B. Trigonal planar
C. Bent 1
D. Bent 2
E. Trigonal pyramidal
21.
A flask contains 1.0 gram of methane, 1.0 gram of oxygen, and 1.0 gram of
sulfur dioxide. The partial pressure of methane is 0.50 atm. What is the total
pressure in the flask?
A. 3.5 atm
B. 1.5 atm C. 1.2 atm
D. 0.88 atm E. 0.44 atm
22.
20.0 grams of sodium hydroxide are dissolved in enough water to make 2.00
liters of solution? What is the molarity of the solution?
A. 0.125
B. 0.250
C. 0.750
D. 1.00
E. 2.00
23.
What is the maximum quantity of water that can be made from a mixture of
10.0 g hydrogen and 16.0 g of oxygen?
A. 9.00
B. 10.0
C. 18.0
D. 36.0
E. 74.0
AP Practice Exam
Page 4
24.
Elements M and fluorine react to form two different compounds. IN the first
reaction0.490 g of M reacts with 1.000 g of fluorine. In the second 0.55 g of M
reacts with 1.000 g of fluorine. Which are possible formulas for the two
compounds?
A.
B.
C.
D.
E.
25.
28.
B.
0.100 M
C. 0.250 M
D. 0.500 M
E. 1.00 M
Which of the following experimental procedures is used to separate two
substances by taking advantage of their differing solubilities?
A.
B.
C.
D.
E.
27.
Second compound
M2F2
MF
M2F3
MF2
M3F
What is the molarity of chloride ion, in 100.0 mL of a 0.500 M barium chloride
solution?
A. 0.050
26.
First compound
MF
MF2
MF2
M2F
M2F3
distillation
filtration
decantation
crystallization
precipitation
Which element reacts most readily with chlorine?
A. lithium
B. carbon
C. nitrogen
D. iodine
E. Neon
Within a family or group in the Periodic Chart, metallic character generally
A. increases with increasing atomic number
B. decreases with increasing atomic umber
C. shows no trend with increasing atomic number
D. increases with increasing ionization energy
E. none of the above
AP Practice Exam
Page 5
29.
Consider 210Po+2. How many protons, neutrons, and electrons does this ion
have?
A.
B.
C.
D.
E.
30.
84
84
84
84
84
protons, 126 neutrons, 82 electrons
electrons, 84 protons, 126 neutrons
neutrons, 126 protons, 82 electrons
neutrons, 84 electrons, 126 protons
electrons, 126 neutrons, 82 protons
The apparatus below is used for which method of physical separation:
A. decantation
31.
B. extraction
C. distillation
D. filtration
E. chromatography
The diagram below is an illustration of which scientist’s work:
A. Thompson
B. Lavoisier
C. Rutherford D. Milliken
E. Dalton
AP Practice Exam
Page 6
32.
Club soda is a(n)
A. homogeneous mixture
B. heterogeneous mixture
C. compound
D. pure substance
E. element
33.
Which of the following has the highest vapor pressure?
A. silver acetate
B. aluminum phosphate
C. magnesium iodide
D. sodium dichromate
E. zinc carbonate
34.
The oxidation number of the phosphorus atom in the phosphate ion is:
A. +1
35.
+3
C. +5
D. -3
E. -1
How many grams of calcium nitrate contains 24 grams of oxygen atoms:
A. (24) (164)
(16) (16)
D. (164) (6) (16)
36.
B.
B. (6) (164) (24)
C. (24) (16) (5) ()
164
E.
(24) (164)
(6) (16)
The molar mass is determined by dissolving 5.00
benzene. The freezing point was lowered by
constant, Kf, for benzene is 5.0oC/m. What
compound?
A. 20.0
B. 50.0
C. 100.0
D.
g of a compound in 50.0 g of
2.5oC. The freezing point
is the molar mass of the
150.0
E. 200.0
37.
What is the formula of a compound formed by combining 50.0 grams of
element X (atomic mass = 100.0) and 32.0 grams of oxygen gas?
A. XO2
B. XO4
C. X4O
D. X2O
E. XO
38.
Element Q occurs in compounds X, Y, and Z. The mass of element Q in one
mole of each compound is as follows:
Compound
Grams of Q in compound
X
38.00
Y
95.00
Z
133.00
Element Q is mostly likely:
A. N
B. O
C. F
D.
Ir
E. Cs
AP Practice Exam
Page 7
39.
Which of the following does NOT show hydrogen bonding?
A. Ammonia, NH3
B. Hydrazine, N2H4
C. Hydrogen peroxide, H2O2
D. Dimethyl ether, CH3OCH3
E. Methyl alcohol or methanol, CH3OH
40.
An oxide is known to have the formula X2O7 and to contain 76.8% X by mass.
Which of the following would you use to determine the atomic mass of X?
76.8
76.8
76.8
A.
B.
C.
! 23.2 $ ! 7 $
! 16.0 $ ! 2 $
! 23.2 $ ! 7 $
#"
&% ' #" &%
#"
&% ' #" &%
#"
& '# &
16.0
2
23.2
7
16.0 % " 2 %
D.
76.8
! 16.0 $ ! 7 $
#"
& '# &
23.2 % " 2 %
E.
! 16.0 $ ! 7 $
#"
& '# &
23.2 % " 2 %
76.8
41.
The volume of a liquid is to be measured. Which of the following cylindrical
flasks would take the most accurate measurement?
A. A flask with 1 mL graduations and a diameter of 1 cm
B. A flask with 1 mL graduations and a diameter of 3 cm.
C. A flask with 5 mL graduations and a diameter of 1 cm.
D. A flask with 5 mL graduations and a diameter of 3 cm.
E. A flask with 10 mL graduations and a diameter of 1 cm.
42.
The empirical formula of a compound is CH2 and its molecular mass is 70.
What is the molecular formula of the compound?
A. C2H2
B. C2H4
C. C4H10
D. C5H10
E. C6H10
43.
2 H2O + 4 MnO4– + 3 ClO2– ® 4 MnO2 + 3 ClO4– + 4 OH–
Which species acts as an oxidizing agent in the reaction represented above?
A. H2O B. ClO4–
C. ClO2–
D. MnO2
E. MnO4–
44. When an aqueous solution of NaOH is added to an aqueous solution of potassium
dichromate, K2Cr2O7, the dichromate ion is converted to
A. CrO42–
B. CrO2
C. Cr3+
D.
Cr2O3
E.
Cr(OH)3
AP Practice Exam
Page 8
45.
Which of the following has the lowest conductivity?
A. 0.1 M Copper (II) sulfate
B. 0.1 M potassium hydroxide
C. 0.1 M Barium chloride,
D. 0.1 M hydrofluoric acid
E. 0.1 M nitric acid
46. To determine the molar mass of a solid monoprotic acid, a student titrated a
weighed sample of the acid with standardized aqueous sodium hydroxide. Which
of the following could explain why the student obtained a molar mass that was
too large?
I. Failure to rinse all acid from the weighing paper into the titration vessel
II. Addition of more water than was needed to dissolve the acid
III. Addition of some base beyond the equivalence point
A. I only
B. III only
C. I and II only
D. II and III only
E. I, II, and III
47. The molecular formula for hydrated iron III) oxide, or rust, is generally written as
Fe2O3 . xH2O because the water content in the hydrate can vary. If a 1 molar
sample of hydrated iron (() oxide is found to contain 108 g of water, what is the
molecular formula for the sample?
A. Fe2O3 . H2O
B. Fe2O3 . 3H2O
C. Fe2O3 . 6H2O
D. Fe2O3 . 10H2O
E. Fe2O3 . 12H2O
48.
If 16.0 g of methane reacts with 16.0 g of oxygen gas. Which of the following
will be true?
A. The mass of water formed will be twice the mass of carbon dioxide formed.
B. Equal masses of water and carbon dioxide will be formed.
C. Equal umbers of moles of water and carbon dioxide will be formed.
D. The limiting reagent will be methane.
E. The limiting reagent will be oxygen.
AP Practice Exam
Page 9
49.
How many grams of carbon are present in 270 g of glucose?
A. 12.0 g
B. 18.0g
C. 67.5 g
D. 72.0 g
E. 108 g
50.
The concentration of sodium chloride in the ocean is about 0.50 molar. How
many grams of sodium chloride are present in 1 kg of sea water.
A. 30 g
B. 60 g
C. 100 g
D. 300 g
E. 600 g
STOP
AP Practice Exam
Page 10
AP Chemistry Midterm 1st Nine Weeks
Section II - Free Response (50%)
PART A - Calculator allowed. (30 points: 10 points each problem)
THE METHOD USED AND THE STEPS INVOLVED IN ARRIVING AT YOUR
ANSWERS MUST BE SHOWN CLEARLY. It is to your advantage to do this, since
you may obtain partial credit if you do and you will receive little or no credit if you do
not. Attention should be paid to significant figures.
1. Answer the following questions relating to gravimetric analysis
In the first of two experiments, a student is assigned the task of determining the umber of moles of
water in one mole of a magnesium hydrate. The student collects the data shown in the following
table:
Mass of empty container
Initial mass of sample and container
Mass of sample and container after first heating
Mass of sample and container after second heating
Mass of sample and container after third heating
22.347
25.825
23.982
23.976
23.977
g
g
g
g
g
a. Explain why the student can correctly conclude that the hydrate was heated a sufficient
number of times in the experiment.
b. Use the data above to
i. calculate the total number of moles of water lost when the sample was heated, and,
ii. determine the formula of the hydrated compound.
c. Annie heats the hydrate in an uncovered crucible, ad some of the solid spatters out of the
crucible. This spattering will have what effect on the calculated mass of the water lost by the
hydrate? Explain.
Anita conducts a second experiment, and is given 2.94 g of a mixture containing anhydrous
magnesium chloride and potassium nitrate. To determine the percentage by mass of magnesium
chloride in the mixture she uses excess silver nitrate to precipitate the chloride ion as silver chloride.
d. Starting with 2.94 g sample of the mixture dissolved in water, briefly describe the steps
necessary to quantitatively determine the mass of the silver chloride precipitate.
e. Anita determines the mass of the silver chloride precipitate to be 5.48 g. On the basis of this
information, calculate each of the following.
i.
The number of moles of magnesium chloride in the original mixture.
ii.
The percent by mass of magnesium chloride in the original mixture
AP Practice Exam
Page 11
2. The molecular formula of a hydrocarbon is to be determined by analyzing its
combustion products and investigating its ideal gas law properties.
(a) The hydrocarbon burns completely, producing 7.2 grams of water and 7.2
liters of carbon dioxide at standard conditions. What is the empirical formula
of the hydrocarbon?
(b) Calculate the mass in grams of oxygen required for the complete combustion
of the sample of the hydrocarbon described in (a).
(c) The hydrocarbon dissolves readily in chloroform, CHCl3. The freezing point of
a solution prepared by mixing 100. grams of chloroform, and 0.600 gram of
the hydrocarbon is -64.0˚C. The molal freezing-point depression constant of
chloroform is 4.68˚C/molal and its normal freezing point is -63.5˚C. Calculate
the molecular weight of the hydrocarbon.
(d) What is the molecular formula of the hydrocarbon?
2 HCOONa + H2SO4

2 CO + 2 H2O + Na2SO4
3. A 0.964 gram sample of a mixture of sodium formate and sodium chloride is
analyzed by adding sulfuric acid. The equation for the reaction for sodium formate
with sulfuric acid is shown above. The carbon monoxide formed measures 242
milliliters when collected over water at 752 Torr and 22.0˚C. Calculate the percentage of sodium formate in the original mixture.
AP Practice Exam
Page 12
PART B - No calculator (20 points total)
For each of the following three reactions, first (a) write a balanced equation for the
reaction and in part (b) answer the question about the reaction. Initially the
coefficients should be in terms of the lowest whole numbers. Assume that
solutions are aqueous unless otherwise indicated. Represent substances in
solutions as ions if the substances are extensively ionized. Omit formulas for any
ions or molecules that are unchanged by the reaction. Box each answer. (6
points)
Example: A strip of magnesium is added to a solution of silver nitrate.
(i) Mg + 2 Ag+
 Mg2+ + 2 Ag
(ii) Which substance is oxidized in the reaction?
Answer: Magnesium (Mg) metal
1. (i) A solution of tin(II) nitrate is added to a solution of potassium
permanganate.
(ii) Which species is the oxidizing agent? How many total electrons are lost in
the complete reaction?
2. (i) solid sodium oxide is added to water
(ii) How would one test the identity of the product, what would be observed?
3. (i) A solution of hydrogen peroxide is catalytically decomposed
(ii) What is the function of the catalyst?
AP Practice Exam
Page 13
Your responses to the rest of the questions in this part of the exam will be
graded on the basis of the accuracy and relevance of the information cited.
Explanations should be clear and well organized. Examples and equations may
be included in your responses where appropriate.
Specific answers are
preferable to broad, diffuse responses. (each question is worth 7 points)
4.
CF4
XeF4
ClF3
(a) Draw a Lewis electron–dot structure for each of the molecules above and
identify the shape of each.
(b) Use the valence shell electron–pair repulsion (VSEPR) model to explain the
geometry of each of these molecules.
(c) Describe the polarity of each and explain your reasoning.
moment.
Define dipole
5. Use the details of modern atomic theory to explain each of the following
experimental observations.
(a)
Within a family such as the alkali metals, the ionic radius increases as the
atomic number increases.
(b)
The radius of the chlorine atom is smaller than the radius of the chloride
ion, Cl-. (Radii : Cl atom = 0.99Å; Cl- ion = 1.81Å)
(c)
The first ionization energy of aluminum is lower than the first ionization
energy of magnesium.
(First ionization energies: 12Mg = 7.6 ev; 13Al = 6.0 ev)
(d)
For magnesium, the difference between the second and third ionization
energies is much larger than the difference between the first and second
ionization energies.
(Ionization energies for Mg: 1st = 7.6 ev; 2nd = 14 ev; 3rd = 80 ev)