Heat of Formation - Questions
The Heat of Formation Concept Builder is comprised of 27 questions. The questions are divided into 10 different Question Groups and spread across three activities. Questions in the same group are rather similar to one another. The Concept Builder is coded to select at random a question from each group until a student is successful with that group of questions.
There are three activities in the Concept Builder. Those three activities are described as follows:
- Equations: Question Groups 1-4 ... Given the heat of formation value for a compound, identify the appropriately written formation or decomposition equation and the corresponding enthalpy change.
- Heat of Reaction 1: Question Groups 5-7 ... Given the heat of formation values for reactants and products, calculate the enthalpy change for a reaction. Includes the simplest cases.
- Heat of Reaction 2: Question Groups 8-10 ... Given the heat of formation values for reactants and products, calculate the enthalpy change for a reaction. Includes the most complex cases.
The questions from each group are shown below. Teachers are encouraged to view the questions in order to judge which activities are most appropriate for their classes. We recommend all three ... in order.
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Heat of Formation
Activity 1: Equations
Question Group 1
Question 1
The standard heat of formation of CH
4(g) is -74.8 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
C
(s) + 2 H
2(g) ==> CH
4(g) ∆H = -74.8 kJ
CH
4(g) ==> C
(s) + 2 H
2(g) ∆H = +74.8 kJ
C
(s) + H
4(g) ==> CH
4(g) ∆H = -74.8 kJ
CH
4(l) ==> CH
4(g) ∆H = -74.8 kJ
C
(g) + 4 H
(g) ==> CH
4(g) ∆H = -74.8 kJ
CH
4(g) ==> C
(s) + 4 H
(g) ∆H = +74.8 kJ
Question 2
The standard heat of formation of C
3H
8(g )is -104 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
3 C
(s) + 4 H
2(g) ==> C
3H
8(g) ∆H = -104 kJ
C
3H
8(g) ==> 3 C
(s) + 4 H
2(g) ∆H = +104 kJ
3 C
(s) + 8 H
(g) ==> C
3H
8(g) ∆H = -104 kJ
C
3H
8(g) ==> 3 C
(s) + 8 H
(g) ∆H = +104 kJ
C
3(s) + 4 H
2(g) ==> C
3H
8(g) ∆H = -104 kJ
C
3H
8(g) ==> C
3(s) + H
8(g) ∆H = +104 kJ
Question 3
The standard heat of formation of CCl
4(l) is -135 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
C
(s) + 2 Cl
2(g) ==> CCl
4(g) ∆H = -135 kJ
CCl
4(l) ==> C
(s) + 2 Cl
2(g) ∆H = +135 kJ
C
(s) + Cl
4(g) ==> CCl
4(g) ∆H = -135 kJ
CCl
4(g) ==> CCl
4(l) ∆H = -135 kJ
C
(g) + 4 Cl
(g) ==> CCl
4(l) ∆H = -135 kJ
CCl
4(l) ==> C
(s) + 4 Cl
(g) ∆H = +135 kJ
Question Group 2
Question 4
The standard heat of formation of H
2O
(g) is -242 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
H
2(g) + ½ O
2(g) ==> H
2O
(g) ∆H = -242 kJ
2 H
2(g) + O
2(g) ==> 2 H
2O
(g) ∆H = -484 kJ
2 H
2O
(g) ==> 2 H
2(g) + O
2(g) ∆H = +484 kJ
2 H
2(g) + O
2(g) ==> 2 H
2O
(g) ∆H = -242 kJ
H
2(g) + O
(g) ==> H
2O
(g) ∆H = -242 kJ
2 H
(g) + O
(g) ==> H
2O
(g) ∆H = -242 kJ
Question 5
The standard heat of formation of C
2H
6(g )is -84.7 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
2 C
(s) + 3 H
2(g) ==> C
2H
6(g) ∆H = -84.7 kJ/mol
C
2(g) + 3 H
2(g) ==> C
2H
6(g) ∆H = -84.7 kJ/mol
2 C
(s) + 6 H
(g) ==> C
2H
6(g) ∆H = -84.7 kJ/mol
C
2(g) + H
6(g) ==> C
2H
6(g) ∆H = -84.7 kJ/mol
C
2H
6(g) ==> C
2(g) + H
6(g) ∆H = +84.7 kJ/mol
C
2H
6(g) ==> 2 C
(s) + 6 H
(g) ∆H = +84.7 kJ/mol
Question 6
The standard heat of formation of Al
2O
3(s) is -1676 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
2 Al
(s) + 3/2 O
2(g) ==> Al
2O
3(s) ∆H = -1676 kJ
4 Al
(s) + 3 O
2(g) ==> 2 Al
2O
3(s) ∆H = -3352 kJ
2 Al
2O
3(s) ==> 4 Al
(s) + 3 O
2(g) ∆H = +3352 kJ
Al
2(s) + O
3(g) ==> Al
2O
3(s) ∆H = -1676 kJ
Al
2O
3(s) ==> Al
2(s) + O
3(g) ∆H = +1676 kJ
2 Al
2(s) + 2 O
3(g) ==> 2 Al
2O
3(s) ∆H = -3352 kJ
Question Group 3
Question 7
The standard heat of formation of BaCO
3(s) is -1216 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
Ba
(s) + C
(s) + 3/2 O
2(g) ==> BaCO
3(s) ∆H = -1216 kJ
2 Ba
(s) + 2 C
(s) + 3 O
2(g) ==> 2 BaCO
3(s) ∆H = -2432 kJ
BaCO
3(s) ==> Ba
(s) + C
(s) + 3/2 O
2(g) ∆H = +1216 kJ
Ba
(s) + C
(s) + O
3(g) ==> BaCO
3(s) ∆H = -1216 kJ
2 BaCO
3(s) ==> Ba
2(s) + C
2(s) + 3/2 O
2(g) ∆H = +2432 kJ
BaCO
3(s) ==> 1/3 Ba
3(s) + 1/3 C
3(s) + O
3(g) ∆H = +1216 kJ
Question 8
The standard heat of formation of CaCO
3(s) is -1207 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
Ca
(s) + C
(s) + 3/2 O
2(g) ==> CaCO
3(s) ∆H = -1207 kJ
2 Ca
(s) + 2 C
(s) + 3 O
2(g) ==> 2 CaCO
3(s) ∆H = -2414 kJ
CaCO
3(s) ==> Ca
(s) + C
(s) + 3/2 O
2(g) ∆H = +1207 kJ
Ca
(s) + C
(s) + O
3(g) ==> CaCO
3(s) ∆H = -1207 kJ
2 CaCO
3(s) ==> Ca
2(s) + C
2(s) + 3/2 O
2(g) ∆H = +2414 kJ
CaCO
3(s) ==> 1/3 Ca
3(s) + 1/3 C
3(s) + O
3(g) ∆H = +1207 kJ
Question 9
The standard heat of formation of MgCO
3(s )is -1096 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
Mg
(s) + C
(s) + 3/2 O
2(g) ==> MgCO
3(s) ∆H = -1096 kJ
2 Mg
(s) + 2 C
(s) + 3 O
2(g) ==> 2 MgCO
3(s) ∆H = -2192 kJ
MgCO
3(s) ==> Mg
(s) + C
(s) + 3/2 O
2(g) ∆H = +1096 kJ
Mg
(s) + C
(s) + O
3(g) ==> MgCO
3(s) ∆H = -1096 kJ
2 MgCO
3(s) ==> Mg
2(s) + C
2(s) + 3/2 O
2(g) ∆H = +2192 kJ
MgCO
3(s) ==> 1/3 Mg
3(s) + 1/3 C
3(s) + O
3(g) ∆H = +1096 kJ
Question Group 4
Question 10
The standard heat of formation of KClO
4(s) is -433 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
K
(s) + ½ Cl
2(g) + 2 O
2(g) ==> KClO
4(s) ∆H = -433 kJ
2 K
(s) + Cl
2(g) + 4 O
2(g) ==> 2 KClO
4(s) ∆H = -866 kJ
K
(s) + Cl
(g) + 2 O
2(g) ==> KClO
4(s) ∆H = -433 kJ
K
(s) + Cl
(g) + O
4(g) ==> KClO
4(s) ∆H = -433 kJ
KClO
4(s) ==> K
(s) + Cl
(g) + O
4(g) ∆H = +433 kJ
2 KClO
4(s) ==> 2 K
(s) + 2 Cl
(g) + 4 O
2(g) ∆H = +866 kJ
Question 11
The standard heat of formation of KNO
3(s) is -495 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
K
(s) + ½ N
2(g) + 3/2 O
2(g) ==> KNO
3(s) ∆H = -495 kJ
2 K
(s) + N
2(g) + 3 O
2(g) ==> 2 KNO
3(s) ∆H = -990 kJ
K
(s) + N
(g) + O
3(g) ==> KNO
3(s) ∆H = -495 kJ
KNO
3(s) ==> K
(s) + N
(g) + 3 O
(g) ∆H =+495 kJ
KNO
3(s) ==> K
(s) + N
(g) + O
3(g) ∆H = +495 kJ
2 KNO
3(s) ==> 2 K
(s) + 2 N
(g) + 6 O
(g) ∆H = +990 kJ
Question 12
The standard heat of formation of HNO
3(l) is -174 kJ/mol. Which of the following chemical equations and corresponding ∆H values are consistent with this fact? Identify all that apply.
½ H
2(g) + ½ N
2(g) + 3/2 O
2(g) ==> HNO
3(l) ∆H = -174 kJ
H
2(g) + N
2(g) + 3 O
2(g) ==> 2 HNO
3(l) ∆H = -348 kJ
H
2(g) + 2 N
(g) + 2 O
3(g) ==> HNO
3(l) ∆H = -348 kJ
HNO
3(l) ==> H
(g) + N
(g) + 3 O
(g) ∆H =+174 kJ
HNO
3(l) ==> H
(g) + N
(g) + O
3(g) ∆H = +174 kJ
2 HNO
3(l) ==> 2 H
(g) + 2 N
(g) + 6 O
(g) ∆H = +348 kJ
Activity 2: Heat of Reaction 1
Activity 2 questions involve multi-part exercises that guide students from knowledge of the heat of formation values to the determination of the heat of reaction. The basic idea of the questions are presented below. However, the actual activity is significantly more sophisticated than a static question on a page.
Question Group 5
Question 13
Determine the enthalpy change of the reaction:
2 CO
(g) + O
2(g) ==> 2 CO
2(g)
∆H
f Values
CO
(g): -110.5 kJ/mol
CO
2(g): -393.5 kJ/mol
Question 14
Determine the enthalpy change of the reaction:
2 H
2O
2(l) ==> 2 H
2O
(l) + O
2(g)
∆H
f Values
H
2O
2(l): -187.8 kJ/mol
H
2O
(l): -285.8 kJ/mol
Question Group 6
Question 15
Determine the enthalpy change of the reaction:
N
2H
4(l) + O
2(g) ==> N
2(g) + 2 H
2O
(g)
∆H
f Values
N
2H
4(l) +50.6 kJ/mol
H
2O
(g): -241.8 kJ/mol
Question 16
Determine the enthalpy change of the reaction:
Fe
3O
4(s) + 4 H
2(g) ==> 3 Fe
(s) + 4 H
2O
(g)
∆H
f Values
Fe
3O
4(s) -1118.4 kJ/mol
H
2O
(g) -241.8 kJ/mol
Question Group 7
Question 17
Determine the enthalpy change of the reaction:
2 KClO
3(s) ==> 2 KCl
(s) + 3 O
2(g)
∆H
f Values
KClO
3(s) -391.4 kJ/mol
KCl
(s) -436.68 kJ/mol
Question 18
Determine the enthalpy change of the reaction:
KClO
4(s) ==> KCl
(s) + 2 O
2(g)
∆H
f Values
KClO
4(s) -430.12 kJ/mol
KCl
(s) -436.68 kJ/mol
Activity 3: Heat of Reaction 2
Activity 3 questions involve multi-part exercises that guide students from knowledge of the heat of formation values to the determination of the heat of reaction. The basic idea of the questions are presented below. However, the actual activity is significantly more sophisticated than a static question on a page.
Question Group 8
Question 19
Determine the enthalpy change of the reaction:
CH
4(g) + 2 O
2(g) ==> CO
2(g). + 2 H
2O
(l)
∆H
f Values
CH
4(g): -74.8 kJ/mol
CO
2(g): -393.5 kJ/mol
H
2O
(l): -285.8 kJ/mol
Question 20
Determine the enthalpy change of the reaction:
C
3H
8(g) + 5 O
2(g) ==> 3 CO
2(g). + 4 H
2O
(g)
∆H
f Values
C
3H
8(g): -74.8 kJ/mol
CO
2(g): -393.5 kJ/mol
H
2O
(g): -241.8 kJ/mol
Question 21
Determine the enthalpy change of the reaction:
2 C
2H
5OH
(l) + 7 O
2(g) ==> 4 CO
2(g). + 6 H
2O
(g)
∆H
f Values
C
2H
5OH
(l): -277.7 kJ/mol
CO
2(g): -393.5 kJ/mol
H
2O
(g): -241.8 kJ/mol
Question Group 9
Question 22
Determine the enthalpy change of the reaction:
HNO
3(g) + 4 H
2(g) ==> NH
3(g) + 3 H
2O
(g)
∆H
f Values
HNO
3(g): -134.3 kJ/mol
NH
3(g): -46.1 kJ/mol
H
2O
(g): -241.8 kJ/mol
Question 23
Determine the enthalpy change of the reaction:
2 CH
3OH
(l) + 3 O
2(g) ==> 2 CO
2(g) + 4 H
2O
(g)
∆H
f Values
CH
3OH
(l) -238.7 kJ/mol
CO
2(g) -393.5 kJ/mol
H
2O
(g) -241.8 kJ/mol
Question 24
Determine the enthalpy change of the reaction:
2 C
2H
2(g) + 5 O
2(g) ==> 4 CO
2(g). + 2 H
2O
(g)
∆H
f Values
C
2H
2(g) +226.7 kJ/mol
CO
2(g) -393.5 kJ/mol
H
2O
(g) -241.8 kJ/mol
Question Group 10
Question 25
Determine the enthalpy change of the reaction:
Al
2O
3(s) + 3 H
2O
(g) ==> 2 Al(OH)
3(s)
∆H
f Values
Al
2O
3(s) -1675.5 kJ/mol
H
2O
(g) -241.8 kJ/mol
Al(OH)
3(s) -1277 kJ/mol
Question 26
Determine the enthalpy change of the reaction:
Fe
2O
3(s) + 3 CO
(g) ® 2 Fe
(s) + 3 CO
2(g)
∆H
f Values
Fe
2O
3(s) -824.2 kJ/mol
CO
(g) -110.5 kJ/mol
CO
2(g) -393.5 kJ/mol
Question 27
Determine the enthalpy change of the reaction:
SiC
(s) + 2 CO
(g) ® SiO
2(s) + 3 C
(s)
∆H
f Values
SiC
(s) -71.5 kJ/mol
CO
(g) -110.5 kJ/mol
SiO
2(s) -910.86 kJ/mol