Chemistry 120
Exam 1
February 23, 2007
Name __________________
SHOW YOUR WORK. NO WORK, NO CREDIT
INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS
Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.
IONS
Group I metals and NH4+
Nitrates, Acetates, Perchlorates
Fluoride
Chlorides, Bromides, and Iodides
Sulfates
Other anions
AX2
AX3
AX2E
AX4
AX3E
AX2E2
Soluble/Insoluble
soluble
soluble
soluble
soluble
soluble
insoluble
Exceptions
none
none
Group II
silver, lead, mercury(I)
strontium, barium, lead
Group I and ammonium salts,
Group II sulfides,
barium oxide & hydroxide,
strontium oxide & hydroxide
trigonal bipyramid
AX6
octahedral
see saw
AX5E
square pyramid
T
AX4E2
square planar
linear
AX3E3
T
AX2E4
linear
linear
AX5
trigonal planar
AX4E
bent
AX3E2
tetrahedral
AX2E3
trigonal pyramid
bent
Enthalpies of Formation (∆Hf) for Selected Species
-59.67 kJ/mole
HC2H3O2 (l) -484.5 kJ/mole
CO (g)
C10H22 (l)
C3H8 (g)
-105 kJ/mole
H2O (g)
-241.8 kJ/mole
CO2 (aq)
C6H6 (l)
+49.0 kJ/mole
H2O (l)
-285.8 kJ/mole
CO2 (g)
-1260 kJ/mole
H2O2 (l)
-187.8 kJ/mole
O (g)
C6H12O6
CH3OH (l)
-238.7 kJ/mole
NH3 (g)
-46.1 kJ/mole
O2 (g)
NH3 (aq)
-80.3 kJ/mole
O3 (g)
C2H5OH (l) -277.7 kJ/mole
1
-110.5 kJ/mole
-413.8 kJ/mole
-393.5 kJ/mole
+249.2 kJ/mole
0 kJ/mole
+143 kJ/mole
I PLEDGE ON MY HONOR THAT DURING THE EXAM I HAVE NEITHER GIVEN NOR
RECEIVED ASSISTANCE NOR HAVE I SEEN ANY DISHONEST WORK.
Signed __________________________________________________________________________
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Multiple choice - circle the correct answer.
1.
(2 pt) What symbol (metric system prefix) is used to represent the factor 10-12?
a) n
2.
b) µ
b) -1
c) +1
b) CH
d) +2
c) C5H4
d) C10H10
79
34 []
79
35 []
78
34 []
81
36 []
A
B
C
D
b) A and D
c) A and B
d) A and C
(2 pt) Which of the drawings represents a mixture?
(a)
a) (a)
7.
d) sulfur (S)
(2 pt) Which of the following represent isotopes ([ ]represents the symbol for the designated atom) ?
a) C and D
6.
c) phosphorus (P)
(2 pt) Give the molecular formula corresponding to the following ball-and-stick molecular representation (structural formula) of
naphthalene (black = C, white = H). In writing the formula, list the atoms in alphabetical order.
a) C10H8
5.
b) silicon (Si)
(2 pt) What is the charge on the Hg in Hg2SO4?
a) -2
4.
d) m
(2 pt) Which of the following elements has chemical properties similar to aluminum?
a) boron (B)
3.
c) p
(b)
b) (b)
(c)
c) (c)
d) none of them
(2 pts) How many orbitals are there in the n = 2 shell (second shell)?
2
a) 2
8.
9.
b) mass is conserved in the reaction
c) 2 mole of Fe3O4 are produced
d) water is the limiting reagent
(2 pt) Which subatomic particle has the smallest mass?
b) carbon
b) B
c) arsenic
d) oxygen
c) C
d) D
b) 2
c) 3
d) 4
(2 pt) Iodine (53I) belongs to which group of the periodic table?
b) halogens
c) alkali metals
d) noble gases
(2 pt) Which of the following numbers has the least number of significant figures?
a) 410000
15.
d) all three have the same mass
(2 pt) How many significant figures are there in the answer for the following problem?
63.1 + 21.5588 + 37 = ?
a) alkaline earth metals
14.
c) a proton
(2 pt) Which grouping of elements, indicated by letter on the periodic table at the right,
represents the d-block elements?
a) 1
13.
b) a neutron
(2 pt) All of the following elements are nonmetals except
a) A
12.
d) 8
a) no Fe is left over
a) hydrogen
11.
c) 6
(2 pt) 8.0 mole of iron is reacted with 8.0 mole of water according to the chemical equation shown below. Which one of the following
statements is false?
3 Fe (s) + 4 H2O (l) ! Fe3O4 (s) + 4 H2 (g)
a) an electron
10.
b) 4
b) 0.50700
c) 6.022 x 1023
d) 0.000201
(2 pt) To the correct number of significant figures, what is the volume in the graduated cylinder?
___________________________
16.
(2 pts) If SeO4-2 is called selenate, what is the formula for hyposelenite?
17.
(3 pts) Write the formula of the compound that results when BiO+1 combines with Fe(CN)6-4.
18.
(3 pts each) Name the following compounds: SO2, Cu3(PO3)2, SrBr2.
19.
(3 pts each) Write the formula for each of the following compounds.
a. potassium periodate
b. monobromine dioxide
c. tin (II) hydroxide
20.
(6 pts) In lab the class is running a series of reactions that use several potentially hazardous chemicals. Groups are working on the
lab benches and are scattered throughout the lab (typical situation for our lab). Your group has finished the experiment earlier than
those groups around you. Is it OK for your group to remove your safety goggles to work on calculations at your lab desk while the
others finish the lab? Explain your reasoning.
21.
(9 pts) The wavelength of infrared light used in a particular remote control is 1.2 µm. What is the energy of one photon of this
radiation?
3
22.
(9 pts) What is the mass percent of oxygen in K3AsO4?
23.
(9 pts) How many atoms of carbon are there in 100 kL of ethanol (C2H5OH)? The density of ethanol is 0.789 g/mL.
24.
Baking soda (NaHCO3) neutralizes battery acid (H2SO4) in aqueous solution by the following reaction:
+
H2SO4
!
Na2SO4
+
H2CO3
NaHCO3
a. (5 pts) Balance the reaction.
b. (9 pts) When excess NaHCO3 was added to 100.0 mL of 0.100 M H2SO4, 5.0 x 10-3 mole of H2CO3 was actually recovered. What
was the percent yield for this reaction?
Chemistry 120
Exam 2
March 16, 2007
Name __________________
Circle the correct answer:
1.
(2 pts) Which one of the following ionic compounds is soluble in water?
a) Ag3PO4
2.
c) NH4ClO2
d) CuS
(2 pts) The spheres below represent atoms of Co, Al, P, Ar (not necessarily
in that order). Which one of these spheres represents an atom of P?
a) sphere a
3.
b) ZnCO3
b) sphere b
c) sphere c
d) sphere d
(2 pts) Which of the following elements is a liquid at room temperature?
a) iodine
b) fluorine
c) bromine
d) chlorine
4.
(2 pts) An element that has the valence electron configuration 2s22p4 belongs to which period and group?
5.
a) period 4, group 2
b) period 2, group 6
c) period 6, group 2
(2 pts) Which of the following elements has the highest first ionization energy?
a) Cs
6.
b) Kr
c) Se
d) Ga
b) 4
c) 5
d) 6
(2 pts) Which of the following ionic compounds is not soluble in water?
a) NaOH
9.
d) Ba
(2 pts) How many subshells are there in the shell with n = 6?
a) 36
8.
c) Sr
(2 pts) Identify the fourth-row element X that forms the ion on the right.
a) As
7.
b) K
d) period 2, group 4
b) CuCl2
c) BaSO4
d) CaS
(2 pts) Which statement is true for the two electromagnetic waves represented at the right? The
x-axis scale is the same for both waves.
(a)
a) Wave (b) has a higher frequency and higher energy than wave (a).
b) Wave (b) has a higher frequency and lower energy than wave (a).
(b)
0
5
10
Time (ms )
c) Wave (b) has a lower frequency and higher energy than wave (a).
4
15
d) Wave (b) has a lower frequency and lower energy than wave (a).
10.
a) about 120°
11.
H
(2 pts) What is the H-N-H bond angle in NH3 (Lewis structure shown) ?
b) about 109.5°
H N
c) about 90°
d) about 180°
c) Rb+1
d) Sr+2
H
(2 pts) Which atom or ion has the smallest radius?
a) Cl-1
b) Kr0
12.
(2 pts each) Name the following compounds.
a. (NH4)2CrO4
b. SnSO3
13.
(2 pts each) Write the formula for each of the following compounds.
a. ammonium acetate
b. dichlorine heptoxide
14.
(6 pts) Label the following binary compounds as ionic, polar covalent, or purely covalent. Then explain your reasoning.
HCl ______________
LiI ______________
O2 ______________
15.
(8 pts) Write the electron configuration for 76Os. You may start with an inert gas core if you wish.
16.
17.
(7 pts each) Draw Lewis structures, including any resonance forms, for: ClO2+1 and RnF4.
(1 pt each) Fill in the blanks for each structure
Br
H
Se H
Br
I
Br
Molecular Shape _______________________
Molecular Shape _______________________
Polar (yes/no)? _______________________
Polar (yes/no)? _______________________
O
F
F
F U F
F F
H C
H
Molecular Shape _______________________
Molecular Shape _______________________
Polar (yes/no)? _______________________
Polar (yes/no)? _______________________
18.
(7 pts) The electron configuration for 41Nb is [Kr] 5s2 4d3. Is +3 expected to be a stable charge for Ru? Explain your reasoning.
19.
(7 pts) Which Lewis Structure below cannot exist as a real molecule? Explain your reasoning.
Br
I
Br
Br
Br
Cl
Br
Br
Br
F
Br
5
Br
20.
While in lab, your lab partner accidentally slops 10 mL of 1 M HCl onto your bare arm.
a. (3 pts) What action should you take?
b. (3 pts) What action should your lab partner take?
21.
(7 pts) What is the molar concentration of sodium ions in a 0.350 M Na3PO4 solution?
22.
(7 pts) The figure on the right shows the resonance structures for cyanate ion
(CNO 1). Use formal charges to identify the better (more important)
structure(s)? Explain your reasoning.
Chemistry 120
O C N
-1
Exam 3
April 16, 2007
O C N
-1
O C N
Name __________________
Circle the correct answer.
1.
(2 pts) The reaction of Pb(NO3)2 + K2SO4 ! PbSO4 + 2 KNO3 is best classified as a(n)
a) precipitation reaction
2.
4.
8.
d) none of the above
c) Pb+2 + 2 NO3-1 + 2 Na+1 + 2 I-1 ! PbI2 + 2 NaNO3
d) Pb+2 + 2 I-1 ! PbI2
(2 pts) When Na2CrO4 (aq) and AgNO3 (aq) are mixed, a red colored precipitate forms which is
b) Na2NO3
c) AgCrO4
d) NaAg
(2 pts) Which species functions as the reducing agent in the following reduction-oxidation reaction 2 P + 3 Br2 !2 PBr3?
b) Br2
c) P+3
d) P
(2 pts) According to the balanced equation shown below, how many moles of MnO4-1 react with 1.00 mole of oxalic acid,
H2 C 2 O4 ?
5 H2C2O4 (aq) + 2 MnO4-1 (aq) + 6 H+1 (aq) !10 CO2 (g) + 2 Mn2+ (aq) + 8 H2O (l)
b) 1.00 mole MnO4-1
c) 0.400 mole MnO4-1
(2 pts) Which of the following compounds is a strong base?
a) H2SO4
b) NH3
c) H2O
d) 2.25 mole MnO4-1
d) Na2O
(2 pts) Three different substances, AX2, AY2, and AZ2, were
dissolved in water in separate beakers with the results shown in the
diagram. (Water molecules are omitted for clarity.) Which of the
substances is the weakest electrolyte?
a) AX2
9.
c) redox reaction
b) Pb(NO3)2 + 2 NaI ! PbI2 + 2 NaNO3
a) 2.00 mole MnO4-1
7.
b) acid base reaction
a) NO3-1 + Na+1 ! NaNO3
a) Br-1
6.
d) none of the above
(2 pts) Which is the balanced net ionic equation for the reaction of Pb(NO3)2 with NaI.
a) Ag2CrO4
5.
c) redox reaction
(2 pts) The reaction of 2 HNO3 + Ba(OH)2 !Ba(NO3)2 + 2 H2O is best classified as a(n)
a) precipitation reaction
3.
b) acid base reaction
b) AY2
c) AZ2
d) all the same
AX2
AY2
AZ2
(2 pts) Tin occurs in two crystal forms, called white tin and grey tin. Based on the data below for the conversion of white
tin to grey tin, the conversion will be
6
-1
Sn(white) ! Sn(gray)
∆H = -2.09 kJ/mole
∆S = -7.41 J/(K·mole)
a) spontaneous at low temperatures and nonspontaneous at high temperatures.
b) nonspontaneous at low temperatures and spontaneous at high temperatures.
c) spontaneous at all temperatures.
d) nonspontaneous at all temperatures.
10.
(2 pts) Predict the products of a reaction between Ba(NO3)2 (aq) and K2SO4 (aq).
a) BaSO3 (s) and KNO2 (aq)
b) BaSO4 (s) and KNO3 (aq)
c) BaSO4 (aq) and KNO3 (aq)
d) Ba(SO4)2 (s) and K2NO3 (aq)
11.
(2 pts) What is the change in oxidation number (charge) for the carbon in the following unbalanced oxidation half reaction?
C 2 H6 ! C 2 H4 O2
a) 6
12.
b) strong bases
d) no change
c) strong electrolytes
b) + 1554 kJ/mole C2H6
d) -259.0 kJ
(a)
(b)
(c)
(d)
(2 pts) Which of the following compounds is a weak acid?
a) NH3
16.
c) + 259.0 kJ
(2 pts) A bicycle pump plunger is drawn half way and the inlet sealed at 20°C (orig.). With the piston allowed to move
freely, the temperature is increased to 50°C. Which diagram most closely represents the position of the piston at 50°C?
orig.
15.
d) weak electrolytes
(2 pts) At constant pressure, the exothermic combustion of 0.1667 mole of C2H6 (g) releases 259.0 kJ of heat. What is ∆H
for the reaction (below)?
2 C2H6 + 7 O2 ! 4 CO2 + 6 H2O
a) -1554 kJ/mole C2H6
14.
c) 4
(2 pts) HBr, HI, HNO3, NaBr, and KNO3 are all classified as
a) strong acids
13.
b) 3
b) H2SO4
c) NaHCO3
d) CH3Cl
(2 pts) Which metal is the worst heat conductor (specific heat in parentheses)?
a) Al (0.90 J/g·deg)
b) Cu (0.39 J/g·deg)
c) Pb (0.16 J/g·deg)
d) Sn (0.222 J/g·deg)
17.
(2 pts each) Name the following compounds.
a. H3PO2
b. CoF2
18.
(2 pts each) Write the formula for each of the following compounds.
a. chloric acid
7
b. tin (IV) cyanide
19.
(8 pts) Balance the following redox reaction that takes place in acidic solution.
IO4-1
+
Mn+2
!
MnO4-1
+
20.
(6 pts) Why are sandals not acceptable footware in a chemistry lab?
21.
(8 pts) Write and balance the net ionic equation.
HNO3 + Pb(ClO2)2 ! Pb(NO3)2 + HClO2
22.
(8 pts) Calculate the ∆H for the reaction below using the ∆Hf values on the front page.
3 C3H8 (g) + 10 O3 (g) ! 9 CO2 (g) + 12 H2O (g)
23.
(8 pts) How many molecules of N2 are in a 500.0 mL container at 780 mm Hg and 135°C?
24.
When 20.00 g of NH3 reacts in the presence of excess O2 according to the following chemical equation in a sealed
calorimeter,
4 NH3 (g) + 5 O2 (g) ! 4 NO (g) + 6 H2O (l)
∆H = +1168 kJ
I-1
a. (6 pts) Will the temperature inside the calorimeter increase or decrease? Explain your reasoning.
b. (8 pts) In a calorimeter heat lost has to equal heat gained. How much heat will be transferred in this reaction?
25.
(8 pts) When 1.000 kg of copper absorbs 2156 J of heat, it temperature rises from 25.0°C to 30.6°C. What is the specific
heat of copper?
Chemistry 120
1.
Exam 4
May 4, 2007
Name __________________
(2 pts) When a liquid is heated at its boiling point, the
a) temperature of the liquid remains the same as long as any liquid is present.
b) covalent bonds are broken, allowing vaporization to occur.
c) temperature of the liquid increases.
d) temperature of the vapor phase increases.
2.
(2 pts) In the drawing of acetaldehyde, CH3CHO, the largest partial positive charge (δ+) occurs
on
a) atom (a)
3.
d) atom (d)
b) NH3
c) CH3NH2
d) Au
(2 pts) Which of the following substances has the highest boiling point?
a) CH3-CH2-CH3
5.
c) atom (c)
(2 pts) Which of the following is an ionic solid?
a) NH4Cl
4.
b) atom (b)
b) Ar
c) CH3-CH2-O-H
d) NaF
(2 pts) The reaction A2 + B2 ! 2 AB has an equilibrium constant Keq = 1.8. The following pictures represent reaction
mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules. Which reaction mixture is
at equilibrium?
8
a) reaction mixture (1)
6.
b) reaction mixture (2)
c) reaction mixture (3)
d) reaction mixture (4)
(2 pts) Which of the following will form an acidic solution when dissolved in water?
a) NH3
7.
b) NaOH
c) FeCl2
d) none are acidic
(2 pts) Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide (balanced reaction below).
Which of the following changes in condition will cause the equilibrium to shift toward the products?
FeO (s) + CO (g) ! Fe (s) + CO2 (g)
a) add FeO
8.
b) add CO
c) raise the temperature
d) add CO2
(2 pts) In the reaction above, the unshaded spheres represent H atoms. Which of the reactants and products are acids?
a) (2) and (3)
9.
b) (1) and (3)
c) (1) and (4)
d) (2) and (4)
(2 pts) Which one of the following salts, when dissolved in water, produces the solution with the highest pH?
a) MgO
10.
d) NaCl
b) HY
c) HZ
d) all have the same Ka value
(2 pts) Which of the following compounds does not exhibit hydrogen
bonding?
a) H2O
12.
c) NaOH
(2 pts) The following pictures represent aqueous solutions of three acids;
water molecules have been omitted for clarity. Which acid has the smallest
K a?
a) HX
11.
b) NH3
b) HF
c) H3C-O-CH3
d) CH3CH2NH3
(2 pts) Which should be most soluble in liquid CO2?
a)
b)
c)
d)
9
13.
(2 pts) As a liquid evaporates at a temperature below its boiling point, the temperature of the liquid
a) increases
14.
c) stays the same
d) decreases at low temperatures, but increases at high temperatures
(2 pts) Which picture on the right best indicates the direction of the dipole moment
in formaldehyde, H2C=O?
a) (1)
15.
b) decreases
b) (2)
c) (3)
d) (4)
(2 pts) In pure liquid methanol, CH3OH, which intermolecular forces are present?
a) Dipole-dipole and ion-dipole forces are present.
b) Dispersion, hydrogen bonding and dipole-dipole forces are present.
c) Only hydrogen bonding forces are present.
d) Dispersion and dipole-dipole forces are present.
16.
(2 pts) One reason ionic compounds do not dissolve well in nonpolar solvents is
that
a) not all cations and anions have the same magnitude of charge and therefore do not form neutral ion pairs.
b) ion-dipole interactions are too large for effective solvation to occur.
c) ion-solvent interactions are not strong enough to solvate the ions in solution.
d) there are no forces of attraction between ions and nonpolar molecules.
17.
(2 pts) What is the equilibrium constant expression (Ksp) for the ionization of insoluble Cu(OH)2 in water?
a) Ksp = [Cu+2][OH-1]2/[Cu(OH)2]
b) Ksp = [Cu+2][OH-1]2
c) Ksp = [Cu(OH)2]/([Cu+2][OH-1]2)
d) Ksp = 1/[Cu+2][OH-1]2
18.
(2 pts) Of these weak acids, which is the weakest?
a) HF with Ka = 3.5 x 10-4
b) HC2H3O2 with Ka = 1.8 x 10-5
c) HC7H5O2 with Ka = 6.5 x 10-5
d) HClO with Ka = 3.5 x 10-8
19.
(2 pts) What statement is most consistent for an acid with a pH = 6?
a) It is twice as strong as an acid with a pH of 3.
b) It is half a strong as an acid with a pH = 3
c) It is one thousandth as strong an acid with a pH of 3.
d) It is one thousand times as strong as an acid with a pH = 3.
20.
(2 pts each) Name the following compounds.
a. HBrO4
b. NH3
21.
(2 pts each) Write the formula for each of the following compounds.
a. Potassium dihydrogen phosphite
b. Acetic acid
22.
(8 pts) Write the equilibrium constant expression for the following balanced, net ionic reaction:
MnO4-1 + 5 Fe+2 + 8 H+1 W Mn+2 + 5 Fe+3 + 4 H2O
23.
(6 pts) Why is it NOT a good idea to store coats and bookbags on the lab benches in lab?
24.
(10 pts) Sodium hydroxide is available commercially as a 50.0% by weight aqueous solution. The density of the solution
is 1.53 g/mL. Calculate the molarity of this sodium hydroxide solution.
10
25.
(10 pts) When K2CO3 is dissolved in water, will the solution be acidic, basic, or neutral? Explain your reasoning, showing
reactions where appropriate.
26.
(10 pts) What is the pH of a 0.000250 M H2SO4 solution?
27.
(10 pts) Calculate the pH for 0.500 M HCN (Ka = 4.9 x 10-10)?
11