Download Thermochemistry Exam Review Questions

Thermochemistry Exam Review Questions
1. What is the term for the thermal energy that is required to change the temperature of one gram of
a substance by 1°C?
A. enthalpy
B. heat capacity
C. heat of reaction
D. specific heat
2. For which of the following equations is the enthalpy change equal to ∆H°f for the product?
A. 2Ca(s) + O2(g) → 2CaO(s)
B. C2H2(g) + H2(g) → C2H4(g)
C. 2C(s) + O2(g) → 2CO(g)
D. 3Mg(s) + N2(g) → Mg3N2(s)
3. Which represents an endothermic process?
A. CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g) ∆H= - 402kJ
B. NO(g) + Cl2(g) + 83.9 kJ → NOCl(g) + Cl(g)
C. P4(s) + 6Cl2(g) → 4PCl3(l) + 1277.2 kJ
D.
4. A sample of aluminum absorbed 9.86 J of heat and its temperature increased from 23.3°C to
30.5°C. What is the mass of the aluminum? (The specific heat of aluminum is 0.90 J/g.°C)
A. 1.5g
B. 8.1g
C. 65g
D. 72g
5. What is the H for the following reaction? (Refer to the data booklet on pg 5)
A.
B.
C.
D.
–114.0 kJ
–28.5 kJ
+57.0 kJ
+778.0 kJ
6. Which one of the following processes is endothermic?
A. CH4(g) + 2O2(g) → CO2(g) + H2O(g)
B. 2H2(g) + O2(g) → 2H2O(g)
C. H2O(g) → H2O(l)
D. H2O(s) → H2O(l)
7. Which statement is true for the reaction between HNO3(aq) and N2H4(l)?
A. 205.2kJ are absorbed per mole of H2O(g) used
B. 315.7kJ are absorbed per mole of N2(g) formed
C. 492.4kJ are released per mole of N2H4(l) formed
D. 615.5kJ are released per mole of HNO3(aq) used
8. Given the two reactions below, what is the ∆H for the reaction,
IF5(g) → IF3(g) + F2(g)?
IF(g) + F2(g) → IF3(g) ∆H= - 390kJ
IF(g) +2F2(g) → IF5(g) ∆H= - 745kJ
A. -1135 kJ
B. 35 kJ
C. 355 kJ
D. 1135 kJ
9. Given the following bond energies: C-C 349kJ/mol C-H 416kJ/mol
C-O 361kJ/mol O-H 466kJ/mol
What is the bonding energy for ethanol, C2H5OH(g)?
A.
B.
C.
D.
1.59 x 10°3 kJ/mol
2.01 x 10°3 kJ/mol
2.84 x 10°3 kJ/mol
3.26 x 10°3 kJ/mol
10. A 10.0 g sample of a substance has 34.8 J of energy added to it and its temperature increases by
25.0C. What is the specific heat capacity of the substance?
A. 0.139 J/gC
B. 0.338 J/gC
C. 0.718 J/gC
D. 0.870 J/gC
11. What is the ∆H°f of hydrogen fluoride?
H2(g) + F2(g)  2HF(g) + 542 KJ
A. -542 kJ
B. -271 kJ
C. +271 kJ
D. +542 kJ’
12. What is the specific heat capacity of a substance if 167 J are needed to change the temperature of
15.0g of it from 25.0°C to 33.0°C?
A. 0.19 J/g∙°C
B. 0.34 J/g∙°C
C. 0.72 J/g∙°C
D. 1.4 J/g∙°C
13. Which represents an exothermic process?
A. 2CO(g) + O2(g)  2CO2(g) ∆H= -566kJ
B. 2H2O(l) H2O2(l) + H2(g) ∆H=384kj
C. N2(g) + O2(g) + 180kJ  2NO(g)
D. This diagram:
Solutions Review Questions
1. Which combination if solid and liquid would likely form a solution?
A. ionic solid and nonpolar liquid
B. ionic solid and polar liquid
C. nonpolar solid and polar liquid
D. polar solid and nonpolar liquid
2. If 300ml of a 2.5 mol/L sugar solution is diluted to 600 mL by the addition of water, which
statement is correct?
A. The concentration of sugar increases to 5.o mol/L
B. The moles of sugar decreases
C. The moles of sugar remains constant
D. The moles of water remains constant
9
Which of the following is true for a saturated solution of salt in water?
A. The rate of crystallization equals the rate of dissolving
B. The rate of crystallization is greater than the rate of dissolving
C. The rate of crystallization is less than the rate of dissolving
D. The rate of crystallization will increase greatly with the addition of a salt crystal
10 A 5.0g sample of sugar is dissolved in 150 mL of water. Respectively, the sugar and water are
called what?
A. solute and solution
B. solute and solvent
C. solution and solvent
D. solvent and solute
11 A precipitate forms when a solution containing an unknown cation is added S2-, but not when a
equal volume is added to SO42-. Which of the following could be unknown cation? (refer to the
solubility table on page 12 of the Chemistry Data Booklet.)
A. NH4B. Na+
C. Pb2+
D. Zn2+
12 What happens when NaCl(s) is dissolved in water?
A. Cl- ions are attracted to the oxygen atoms of the water molecules
B. Cl- ions are repelled by the hydrogen atoms of the water molecules
C. Na+ ions are attracted to the oxygen atoms of the water molecules
D. Na+ ions are repelled by the oxygen atoms of the water molecules
13 Which of the following would produce a precipitate when equal volumes of 0.5 mol/L of
aqueous solutions of each are mixed? (Refer to the Data Booklet, page 12)
A. AgNO3 and NaCl
B. BaCl2 and KNO3
C. NaOH and H2CO3
D. (NH4)2CO3 and K2SO4
14 What is the concentration of a solution if 3.4g of NH3 is dissolved in enough water to make
500mL of solution?
A. 4.0 x 10-4 mol/L
B. 6.8 x 10-3 mol/L
C. 0.40 mol/L
D. 6.8 mol/L
15 What is the concentration of a solution of sulphuric acid that is prepared by the dilution of
150mL of 5.00mol/L H2SO4 to 2.00L?
A. 0.150 mol/L
B. 0.375 mol/L
C. 0.500 mol/L
D. 0.750 mol/L
16 Which combinations of solid and liquid would likely form a solution?
I. ionic solid and nonpolar liquid
II. ionic solid and polar liquid
III. nonploar solid and nonpolar liquid
IV. nonpolar solid and polar liquid
A. I and III
B. I and IV
C. II and III
D. II and IV
17 What is the definition of molarity of a solution?
A. moles of solute per kilogram of solution
B. moles of solute per kilogram of solvent
C. moles of solute per litre of solution
D. moles of solute per litre of solvent
Chemical Kinetics Review Questions
1. The potential energy diagram for the reaction, Br + H2 → HBr + H, is:
What is the activation energy for the reverse reaction?
A. 0 kJ/mol
B. 12 kJ/mol
C. 105 kJ/mol
D. 117 kJ/mol
2. The potential energy diagram for the reaction, Br + H2 ↔ HBr + H, is (diagram #3) What is the
activation energy for the forward reaction?
A.
B.
C.
D.
0 kJ/mol
12 kJ/mol
105 kJ/mol
117 kJ/mol
3. Three different substances, A, B, and oxygen, are mixed. A two-step reaction occurs as shown
below.
1) A + O2 → AO2
2) B + AO2 → A + BO2
Which substance is the catalyst?
A. A
B. AO2
C. B
D. BO2
4. Which one of the following will lower the activation energy for a reaction?
A. adding a suitable catalyst to the reaction
B. adding more reactants to the reaction
C. increasing the pressure on the reactants
D. increasing the temperature of the reactants
5. Consider the following reactants:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Which of the following changes would increase the rate of the reaction?
A. increase the surface area of Zn
B. increase the volume of H2
C. decrease the [HCl]
D. decrease the temperature
6. Which one of the following statements concerning chemical reactions is true?
A. A catalyst increases the activation energy of a reaction
B. A reaction occurs every time reactant molecules collide
C. The reaction rate is fast for a reaction with a high activation energy
D. The slowest step in a reaction mechanism determines the rate of a reaction
14. Which one of the following will lower the activation energy for a reaction?
A. adding a suitable catalyst to the reaction
B. adding more reactants to the reaction
C. increasing the pressure on the reactants
D. increasing the temperature of the reactants
21. The potential energy diagram for the reaction Br + H2 ↔ HBr + H, is:
A.
B.
C.
D.
What is the heat of reaction for the forward reaction?
-117 kJ/mol
-105 kJ/mol
+105 kJ/mol
+117 kJ/mol
Equilibrium Review Questions
1. Which describes a carbonated beverage at equilibrium in a soft drink bottle?
A. closed system with constant observable properties.
B. closed system with variable observable properties.
C. open system with constant observable properties.
D. open system with variable observable properties.
2. At the equilibrium [N2H4] = 0.10 mol/L, [N2] = 0.10 mol/L, [H2]mol/L. What is the numerical
value of the equilibrium constant?
a.
b.
c.
d.
N2H4(g) ↔ N2(g) + 2H2(g)
0.040
0.20
5.0
25
3. The reaction: 2S(s) + 3O2 (g) ↔ 2SO3(g) + 800 kJ has reached the equilibrium in a closed
container. Which change will shift the equilibrium to the right?
A. adding a catalyst without changing the temperature or pressure
B. increasing the pressure by reducing the volume
C. increasing the temperature without changing the pressure
D. removing oxygen gas from the system
4. Which statements are true for an equilibrium constant expression?
I. Gases and dissolved ions are included in the expression
II. Pure liquid and solids are NOT included in the expression
III. The product appear in the denominator
A. I and II
B. I and III
C. II and III
D. I, II, and III
5. Consider the following reaction: N2(g) + 2O2(g) ↔ 2NO2(g)
At the equilibrium the [N2] = 0.400 mol/L, [O2] = 0.200 mol/L, and [NO2] = 0.100 mol/L.
What is the numerical value of the equilibrium constant Keq?
A. 0.125
B. 0.625
C. 1.25
D. 1.60
6. If a chemical reaction is to be considered a case of a dynamic equilibrium, the system must be
closed and the macroscopic empirical properties must be constant. What OTHER criterion must
also exist?
A. The container must be sealed
B. There must be evidence of reversibity
C. There must be more than one state of matter in the system
D. There must be no chemical reactions occurring in the system
7. The reaction NO(g) + O3 ↔ NO2(g) + O2(g) is at equilibrium when some of the NO2 gas is
removed from the reaction container. Which statement correctly describes the change that would
result when equilibrium is restored?
A.
B.
C.
D.
The concentration of O2 decreases
The concentration of O3 decreases
The concentration of NO increases
The numerical value of the equilibrium constant decreases
8. Assuming that the system is at equilibrium, which of the following would produce the smallest
concentration of products from 1.00 mol/L initial reactants concentration?
A. C(s) + 2H2(g) ↔ CH4(g)
Keq = 27.5
B. 2C(s) + O2(g) ↔ 2CO(g)
Keq = 1 x 10*6
C. 2Cl2(g) + 2H2O(g) ↔ 4HCl(g)
Keq = 1 x 10*-15
D. FeO(s) + CO(g) ↔ Fe(s) + CO2(g)
Keq = 0.403
9. A quantity of HI(g) was put into an empty flask and was allowed to come to equilibrium
according to this equation:
2HI(g) ↔ H2(g)+I2(g)
What will be the result if a sample of H2(g) is added to the system at equilibrium?
A. [HI] decreases and [I2] decreases
B. [HI] decreases and [I2] increases
C. [HI] increases and [I2] decreases
D. [HI] increases and [I2] increases
10. Consider the following equilibrium: CO(g) + H2 ↔ CO2(g) + H2(g) Keq = 5.0
At equilibrium [CO] = 0.20 mol/L, [H2] = 0.3 mol/L, and [H2] = 0.0 mol/L. What is the
equilibrium [CO2]?
A. 0.013 mol/L
B. 0.066 mol/L
C. 0.33 mo/L
D. 1.0 mol/L
11. What is the equilibrium constant expression for this equation: CO2(g) + C(s)  2CO(g)?
A. Keq = [CO2][C]
[CO]2
B. Keq = [CO]2
[CO2][C]
C. Keq = [CO]2
[CO2]
D. Keq = [CO2]
[CO]2
12. Which would definitely increase the concentration of NO2(g) present at equilibrium in this
reaction? 2NO(g) + O2(g) ↔ 2NO2(g) + 113 kJ
A. adding a catalyst
B. adding NO(g)
C. increasing the volume
D. increasing the temperature
13. Assume that the following system has reached equilibrium in a closed container. Which of the
following changes will produce a greater yield by shifting the equilibrium to the right?
S8(s) + 12O2(g)  8SO3(g)
ΔH = -3166 kJ
A. addition of a catalyst
B. increase the pressure
C. increase the temperature
D. remove O2(g)
14. Which will cause an increase in the numerical value of the equilibrium constant for this reaction?
C(s) + 2H2(g) ↔ CH4(g) + 75 kJ
A. decreasing the temperature
B. decreasing the volume
C. finely powdering the C(s)
D. increasing the [H2]
15. At equilibrium in this gaseous system: 2A + B ↔ AC + D
[A] = 2.00, [B] = 1.20, [C] = 3.00
and [D] = 0.6000. What is the numerical value of the equilibrium constant?
A. 4.32
B. 1.33
C. 1.12
D. 0.889
16. What is the equilibrium constant expression for the reaction, CaCO3(s) ↔ CaO(s) + CaO2(g)?
A. K= [CO2]
B. K= __[CaO]__
[CaCO3]
C. K = ___[CaCO3]__
[CaO] [CO2]
D. K = ____[CaO] [CO2]____
[CaCO3]
17. The equilibrium: CO(g) + H2O(g) ↔ CO2(g) + H2(g)
K=0.50
Is established in a one-litre container. If 2.0 mol of CO and 3.0 mol of H2O are in equilibrium
with 4.0 mol of H2, how much CO2 is present?
A. 0.33 mol
B. 0.75 mol
C. 2.0 mol
D. 3.0 mol
Acid – Base Review Questions
1. Which property is characteristic of solutions of both strong acids and strong bases?
A. are good conductors of electricity
B. have a pH of 7
C. react with zinc to produce hydrogen gas
D. turn red litmus blue
2. Which phrase describes a weak aqueous acid?
E. highly dissociated
F. partially ionized
G. unreactive with zinc
H. very dilute
3. The concentration of H3O+ in a solution is 2.6x 10-3 mol/L at 25C. What is the concentration of OHin the solution?
A. 2.6 x 10-17 mol/L
B. 3.8 x 10 –12 mol/L
C. 3.8 x 10-10 mol/L
D. 2.6 x 10-3 mol/L
4. According to the Bronsted-Lowery concept, how would a substance that can act as an acid in some
reactions and as a base in other reactions be classified?
A. acid-base pair
B. amphiprotic
C. conjugate
D. neutral
5. A 25.00mL sample of KOH(aq) is titrated with 15.23 mL of 0.2250 mol/L HNO3(aq). What is the
concentration of the KOH(aq)?
A. 0.02872 mol/L
B. 0.1371 mol/L
C. 0.3693 mol/L
D. 0.5223 mol/L
6. In a titration experiment, 18.62 mL of 0.0975 mol/L HNO3 acid was needed to completely neutralize
20.0mL of KOH(aq). What was the concentration of the KOH(aq)?
A. 0.00191 mol/L
B. 0.00382 mol/L
C. 0.0908 mol/L
D. 0.105 mol/L
7. Which solution would have the lowest pH?
A. 0.1 mol/L CH3COOH (aq)
B. 0.1 mol/L HCl(aq)
C. 0.1 mol/L NaOH(aq)
D. 0.1 mol/L NH3(aq)
8. Which are the Bronsted-Lowry bases in this reaction?
HCOO-(aq) + H2O(l) ↔ HCOOH(aq) + OH-(aq)
A. HCOO and HCOOH
B. HCOO- and OHC. H2O and HCOOH
D. H2O and OH9. Which statement are true for an aqueous solution with pH = 8.72?
I. [H3O+] = 1.9 x 10-9
II. [OH-] = 5.8 x 10-6
III. solution is a base
A. I and II
B. I and III
C. II and III
D. I, II, and III
10. What is the pH of a 0.30 mol/L HCl solution?
A. 0.52
B. 1.52
C. 3.00
D. 3.51
11. A student found that orange IV indicator turned yellow and methyl orange turned red in samples of
an unknown solution. What is the pH for the unknown solution likely to be?
A. 1.2
B. 3.0
C. 5.3
D. 9.0
12. What is the name of the ion when a positively charged proton combines with a water molecule?
A. ammonium ion
B. hydrogen ion
C. hydronium ion
D. hydroxide ion
13. What is the term for a substance that can react as either a Bronsted-Lowry acid or base?
A. amphoteric
B. buffer
C. indicator
D. neutral
14. What is a characteristic of aqueous solution of both strong acids and strong bases?
A. conduct electricity
B. contain an excess of OHC. react with copper to produce hydrogen gas
D. turn litmus paper red
15. Which type of titration is represented by this curve? (diagram #4)
A. strong acid - strong base
B. strong acid - weak base
C. weak acid - strong base
D. weak acid - weak base
16. How would a 0.10 mol/L solution of HBr be described?
A. concentrated and strong
B. concentrated and weak
C. dilute and strong
D. dilute and weak
17. When the indicator thymol blue is added to a 0.10 mol/L solution of an unknown aid, the solution is
red. What is the acid?
A. HCN
B. HF
C. HNO3
D. H2S
18. 37. What is the [H3O+] in a solution with pOH = 5.20?
A. 1.4 x 10-14 mol/L
B. 1.6 x 10-9 mol/L
C. 6.3 x 10-6 mol/L
D. 7.1 x 10-10 mol/L
19. Which of the following combinations would produce the above titration curve?
A. strong acid added to a strong base
B. strong acid added to a weak base
C. strong base added to a strong acid
D. strong base added to a weak acid
20. What could be the pH of acid rain?
A. 5.0
B. 7.0
C. 9.0
D. 11.0
21. According to the Brønsted-Lowry theory what does an acid do?
A. acts as a proton acceptor in any system
B. acts as a proton donor in any system
C. decreases [H+] in an H2O solution
D. increases [H+] in an H2O solution
22. What is a Brønsted-Lowry acid?
A. an electron acceptor
B. an electron donor
C. a proton acceptor
D. a proton donor
Electrochemistry Review Questions
1. What happens to the reducing agent in an oxidation-reduction reaction?
A. It is oxidized as it gains electrons.
B. It is oxidized as it loses electrons.
C. It is reduced as it gains electrons
D. It is reduced as it loses electrons
2. The cell potential. E°, for an oxidation-reduction reaction was found to equal +1.10V. What can
be said about this reaction?
A. at equilibrium
B. endothermic
C. nonspontaneous
D. spontaneous
3. The diagram above shows the electrolysis of molten KCl. What occurs when the swtich is
closed?
A. positive ions move towards the anode and gain electrons
B. positive ions move towards the anode and lose electrons
C. positive ions move towards the cathode and gain electrons
D. positive ions move towards the cathode and lose electrons
4. Considering the following standards reduction potentials:
2H+ 2e- → H2
E° = 0.00V
Sn2+ + 2e- → Sn
E°= -0.14V
2+
Cd + 2e → Cd
E°= -0.40V
Which pair of substances will react spontaneously?
A. Sn with Cd2+
B. Cd2+ with H+
C. Cd with H2
D. Cd with Sn2+
5. What does the reducing agent do in an oxidation-reduction reaction?
A. gains electrons from the oxidizing agent
B. loses electrons to the oxidizing agent
C. is always reduced
D. is reduced by the oxidizing agent
6. In these incomplete half-reactions which could be an oxidizing agent?
Ag(s) → Ag+(aq)
Cl-(aq) → Cl2(g)
Fe3+(aq) → Fe2+(aq)
Sn2+(aq) → Sn4+(aq)
A. Ag(s)
B. Cl-(aq)
C. Fe3+(aq)
D. Sn2+(aq)
7. What is the oxidation number of nitrogen in nitric acid, HNO3?
A.
B.
C.
D.
+2
+3
+4
+5
8. In an electrochemical cell, electrons travel in which direction?
A. from the anode to the cathode through the external circuit
B. from the anode to the cathode through the porous cup
C. from the cathode to the anode through the external circuit
D. from the cathode to the anode through the porous cup
9. In the reaction of Sn2+ with ClO3- to form Cl- and Sn4+ in acid solution, what is the change in the
oxidation number of Cl?
A. a decrease of 6
B. a decrease of 4
C. a decrease of 2
D. an increase of 2
10. What is the oxidation number of phosphorus in NaH2PO4?
A. –3
B. +1
C. +3
D. +5
11. In the following reaction, which species is the reducing agent?
3Cu(s) + 6H+(aq) + 2HNO3(aq)  3Cu2+(aq) + 2NO(g) + 4H2O(l)
A.
B.
C.
D.
Cu
H+
H in HNO3
O in HNO3
12. Which of the following species are oxidizing agents: K(s), MnO4-(aq), F2(g), H2(g)?
A. H2(g) only
B. F2(g) and H2(g)
C. MnO4-(aq) and F2(g)
D. K(s), MnO4-(aq) and F2(g)
13. Which species has the highest oxidation number for manganese?
A. MnO2
B. MnO4C. Mn2O3
D. MnSO4