SCH4U February 2014
The combustion of methanol is shown by the following equation: a) Using the data below, find the heat of reaction for the combustion of methanol.
C
(s)
+ O
2(g)
 CO
2(g)
2H
2(g)
+ O
2(g)
 2H
2
O
(g)
ΔH = -393 kJ
ΔH = -484 kJ
2C
(s)
+ 4H
2(g)
+ O
2(g)
 2CH
3
OH
(l)
ΔH = -476 kJ b) What is the molar enthalpy of combustion for methanol? c) Express the energy changes for the target reaction in the form ΔH x
= d) Draw the potential energy diagram to illustrate the energy changes for the target reaction. e) Write the target reaction that includes the heat term in the equation. f) What mass of water could be heated from 20.0
0 C to 35.0
held in a calorimeter with a heat capacity of 2.9 kJ/ o C?
0 C by the burning of 10.0 g of methanol that is g) Will ΔS increase or decrease in the combustion of methanol? Will ΔS be positive or negative? h) Calculate the change in entropy for the combustion of methanol. i) Consider your values of ΔH and ΔS. Will the combustion of methanol always be spontaneous? Explain. j) Calculate the change in Gibb’s free energy for the combustion of methanol at 100 o C. Is the reaction spontaneous or non-spontaneous at this temperature? Explain your choice.
2.
Consider the reaction:
NH
4
Cl
(s)
 NH
3(g)
+ HCl
(g)
What are the temperature requirements for the above reaction to work?
3.
The molar enthalpy of combustion of butane is -2871 kJ/mol. What is the molar enthalpy of formation of butane? HINT: first write out the balanced equation for the combustion reaction
1

1.
Excellent questions from the textbook: Chapter 6 Self-Quiz #’s 1-18 on page 407 and Unit 3 Self-Quiz
# 20-30 on page 412 as well as Chapter 6 Review questions (especially #13) on page 408
2.
The following data were collected for the reaction: SO
2
Cl
2

SO
2
+ Cl
2
[SO
2
Cl
0.140
0.120
2
] (mol/L) Time (s)
0
20
0.080
0.070
0.055
0.040
100
130
200
300
0.032
0.028
400
500
0.025 700 a) Graph concentration vs time. b) Determine the rate of reaction when [SO
2
Cl
2
] = 0.120 M, 0.080M and 0.040M. c) Fill the information from (b) into the chart:
Rate of reaction (mol/L.s) [SO
2
Cl
2
] mol/L
0.040
0.080
0.120 d) Determine the rate law for the reaction.
3.
The following data was collected for the reaction: 2NO
(g)
+ O
2(g)

2NO
2(g)
[O
2
] mol/L
0.0010
0.0040
0.0040
[NO
(g)
] mol/L
0.0010
0.0010
0.0030
Initial rate of formation of
NO
2
(mol/L.s)
7.1
28.4
85.2 a) What is the rate law? b) What is the value of the rate constant? c) When the rate of formation of NO
2
is 7.1 mol/L.s, what is the rate of disappearance of O
2
? NO? d) Is it reasonable to suggest that this reaction proceeds as a 1-step reaction? e) If the reaction proceeds as a 2-step mechanism, propose a mechanism that is consistent with the rate law.
4.
The following data was collected for the reaction: 2P + 3Q + R

T + 2U
Trial #
1
2
3
[P] (mol/L) [Q] (mol/L) [R]
(mol/L)
1.0
1.0
1.0
2.0
1.0
2.0
1.0 2.0 3.0
Rate of formation of T (mol/L.min)
3.0
6.0
6.0
2

4
5
6
1.0
2.0
3.0
3.0
3.0
3.0
4.0
5.0
6.0
9.0
36
81 a) What is the rate law? b) What is the effect on the rate of i) doubling [P] ii) tripling [Q] iii) quadrupling [R]
iv) increasing temperature? c) What is the overall order of the reaction? d) Determine the rate constant. e) What is the rate of formation of T when [P] = 4.0 M, [Q] = 3.0 M and [R] = 3.0 M?
5.
Draw a potential energy diagram for the reaction: A + B  C using the following information. a) The mechanism consists of one elementary step. b) The reaction is endothermic. c) The activation energy for the reaction has a value 3x the enthalpy value of the reaction.
6.
Consider the following reaction: N
2(g)
+ 3H
2(g)
 2NH
3(g).
Suppose the reaction is first order in N
2 and first order in H
2
, a) Write the rate law. b) Propose a probable mechanism?
7.
A reaction has the following mechanism:
2NO
2

NO
3
+ NO (slow)
NO
3
+ CO

NO
2
+ CO
2
(fast) a) What is the rate law? b) What is the overall reaction? c) The overall reaction has an enthalpy change of -228 kJ/mol. Draw the potential energy diagram for the overall step. d) Draw a potential energy diagram for the 2-step reaction if ∆H = -100 kJ for step one and ∆H for step two is -128 kJ.
1. The dissociation of ammonia at 27 o C has a K eq
value of 2.63 x 10 -9 .
Heat + 2NH
3(g)

N
2(g)
+ 3H
2(g) a) If 1.00 M ammonia is placed in a reaction vessel, calculate the equilibrium concentrations of N
2
and H
2
. b) What is the percent yield of N
2(g)
? c) Without adding more ammonia, what three things could be done to increase the yield of N
2
? d) What is the equilibrium constant for the reaction:
N
2(g)
+ 3H
2(g)
 2NH
3(g)
?
2. 0.20 moles each of A, B and C are mixed into a 2.0 L container and allowed to react according to the following equation: A
(g)
+ B
(g)
 C
(g)
K eq
= 1.0 x 10 -6 . Calculate the equilibrium concentrations of each gas.
3

3. Consider the following equilibrium:
NH
3(aq)
+ H
2
O
(l)
 NH
4
+
(aq)
+ OH -
(aq)
At equilibrium, the concentrations of NH
3(aq)
, NH
4
+
(aq)
and OH -
(aq)
are 1.00M, 0.0010M and 0.018M respectively. To 500 .0 mL of this equilibrium mixture, 0.050 mol of OH are added. Calculate the new equilibrium concentrations of NH
4
+ and OH -
.
4. Chapter 7 Self Quiz #1-5, 7-14, 18
Chapter 7 Review #11-16
Unit 4 Self-Quiz #1-6, 9
Unit 4 Review #1-4, 7-15
5. What is the K sp
of PbCl
2
if, in a saturated solution of lead (II) chloride, the [Cl ] is 0.032 mol/L?
6. The solubility of calcium sulfate is 0.67 g/L. Calculate the K sp
for calcium sulfate.
7. The solubility of copper (II) hydroxide is 1.8 x 10 -6 g/100 mL. Calculate the K sp
for Cu(OH)
2
.
8. Calculate the calcium ion concentration in a saturated solution of calcium carbonate.
9. What is the solubility, in g/L, of calcium phosphate? K sp
for calcium phosphate is 1.2 x 10 -26 .
10. Which is more soluble, calcium fluoride or silver chloride?
11. The concentration of Ag + in a saturated solution of Ag
2
CrO
4
is 1.5 x 10 -4 mol/L. Calculate the K sp
for Ag
2
CrO
4
.
12. 1.0 x 10 -3 moles of Ba 2+ are added with 6.0 x 10 -3 moles of SO the solution?
4
2 to make a 1 L solution. What is the nature of
13. If 2.00 mL of 0.200M NaOH are added to 1.00 L of 0.100M CaCl
2
, will a precipitate form?
14. How much precipitate of BaCO3 will form when 20.0 mL of 0.10 M Ba(NO
3
)
2
is added to 50.0 mL of 0.10 M
Na
2
CO
3
?
15. Consider #10. When equilibrium is reached, what will a) [CO
3
2] be? b) [Ba 2+ ] be?
16. What mass of BaSO
4
precipitate will form when 50 mL of 0.10M Na
2
SO
4
is mixed with 50 mL of 0.20 M BaCl
2
?
17. Calculate the molar solubility of BaSO
4
in a) pure water b) in 1.0 M SO
4
2.
18. Calculate the molar solubility of AgCl in a 1.0 L solution containing 10.0 g of CaCl
2
.
19. How many grams of CaCO
3
will dissolve in 300 mL of 0.050 M Ca(NO
3
)
2
?
4

20. a) Calculate the molar solubility of MgF
2.
b) Calculate the solubility of MgF
2
in g/100 mL. c) How many grams of MgF
2
will dissolve in a 350 mL solution of 0.25 M NaF? d) If 50 mL of 0.50 M solution of CaCl form? K sp
for CaF
2
is 3.9 x 10
2
are added to 250 mL of a saturated solution MgF
2
, will a precipitate
-11 . Show your calculations.
K a
and K b
1.
Calculate the K a
and percent ionization for 0.50M HNO
2
if the pH is 1.7.
2.
Calculate the pH of 0.015M hydrazine, N
2
H
4
. K b
for hydrazine is 9.6 x 10 -7 .
3.
The percent ionization of 0.10M methanoic acid is 4.2%. Calculate K a
for methanoic acid.
4.
Calculate [H + ], [H
2
C
6
H
5
O
7
], [HC
6
H
5
O
7
2], [C
6
H
10 -4 , K a2
= 1.7 x 10 -5 , K a3
= 6.3 x 10 -6
5
O
7
3] in a 0.10M solution of citric acid, H
3
C
6
H
5
O
7
. K a1
= 7.1 x
K w
and Conjugate Acid-Base Pairs
5.
What is the conjugate base of a) HOCl? b) CH
3
CO
2
H? c) HNO
2
? d) HCO
3
? e) H
2
PO
4
?
Determine K b
for each.
6.
What is the conjugate acid of: a) b) c)
N
2
H
HCO
PO
4
4
3-
?
3
-
?
?
Determine K a
for each.
Hydrolysis of Salts
7.
Will solutions of the following salts be acidic, basic or neutral? a) NH
4
CH
3
COO b) Na
2
SO
4 c) K
2
HPO
4 d) NH
4
Cl e) NaCN
8.
A 0.250M solution of sodium ascorbate, Na
2
C
6
H
6
O
6
, has a pH of 8.65. Calculate K b
for the ascorbate ion.
9.
Calculate the pH of 0.20M solution of NaCN
10.
Titration
5

a) If 250.0 mL of 0.300M Ca(OH) of HNO
2(aq)
?
2
is required to titrate 600.0 mL of HNO
2(aq)
, what is the concentration b) What is the pH of the equivalence point? c) What would be an effective acid-base indicator to use?
11.
A 8.24 g sample of a solid organic acid is dissolved in water. It is found that 47.3 mL of 0.100 M NaOH are needed to titrate the acidic solution. Assuming that there is only one hydrogen in the acidic solid, determine the molar mass of the solid acid. What would the molar mass be if the acid has two hydrogens?
12.
30.0 mL of 0.10M HCl is added to 30.0mL of 0.15M NaOH. What is the resulting pH of the solution?
1.
Compare the following terms: a) Orbit, orbital b) Bohr’s model of the atom, quantum mechanical model c) Polar molecule, non-polar molecule d) Electron configuration, orbital diagram e) P orbital, s orbital, hybrid orbital f) London forces, dipole-dipole forces g) Dipole-dipole forces , hydrogen bonding h) Covalent bond, VanderWaals forces
2.
Draw the electron configuration for: a) manganese b) antimony (short form) c) the phosphorus ion
3.
Draw the orbital diagram for: a) Titanium (short form) b) Fe 2+ c) Carbon in its promoted state
4.
Draw the orbital diagram for: a) Potassium’s 19 th electron b) Valence electrons of aluminum
5.
Draw the bonding orbitals and label the orbitals for: a) PBr
3 b) SiCl
4 c) CH
3
F
6

6.
Draw structural diagrams for: a) O
3 b) HNO
3 c) HCN
7. Draw and name 3-D shape for:
a) HCN
b) CO
3
2-
c) PBr
3
d) SiCl
4
e) PBr
5
f) SF
4
g) SF
6
h) BrCl
3
i) XeF
2
j) XeF
4
8. Determine whether each of the compounds in #7 is polar.
10. Which compounds in #7 required electrons to be promoted to form a hybrid orbital? Name the hybrid orbital formed.
11. Determine the predominant intermolecular force acting on each substance in #7.
12. Consider the following pairs. Predict which has the higher boiling point. State the main reason why. a) XeF
2
, XeF
4 c) CH
2
Cl
2
, CCl
4 b) H d) H
2
, F
2
2
O, H
 Try also the self-quizzes for chapters 3 and 4 and Unit 2
2
S
7