Hess's Law - Questions
The Hess's Law Concept Builder is comprised of 27 two-step questions organized into 9 Question Groups and spread across three difficulty levels. There are three questions in every Question Group. Students will receive one question from each Question Group. Every question involves the same task: use Hess's Law to determine the ∆H of the
target equation. Before performing calculations, students must manipulate and add two or three given equations such that they add up to yield the
target equation.
Here is the breakdown of the difficulty levels:
- Apprentice Difficulty Level: Question Groups 1-3 ... Students are given two equations with the corresponding ∆H value. Equations include fictional species A, B, C, ... . The equations must be added to yield the target equation. They students calculate the ∆H value.
- Master Difficulty Level: Question Groups 4-6 ... Students are given three equations with the corresponding ∆H value. Equations include fictional species A, B, C, ... . The equations must be added to yield the target equation. They students calculate the ∆H value.
- Wizard Difficulty Level: Question Groups 7-9 ... Students are given two or three equations with the corresponding ∆H value. Equations include real substances. The equations must be added to yield the target equation. They students calculate the ∆H value.
The questions from each group are shown below. Teachers are encouraged to view the questions in order to judge which difficulty levels are most appropriate for their classes. Alternatively, teachers can do the
Concept Builder to gain a feel for the student experience..
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Hess's Law
Hess's Law Questions
Question Group 1
Question 1
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
A + 2 C ==> D + E ∆H = -200 kJ
3 C ==> 2 D ∆H = +350 kJ
Target:
3 A + D ==> 3 E ∆H = ???
Question 2
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
3 A + E ==> 2 B ∆H = -150 kJ
2 A + E ==> B + D ∆H = +200 kJ
Target:
A + E ==> 2 D ∆H = ???
Question 3
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 B + E ==> C + D ∆H = +250 kJ
B + 2 E ==> 2 C ∆H = -100 kJ
Target:
2 D ==> 3 B ∆H = ???
Question Group 2
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Question 4
Given:
E + C ==> 2 A ∆H = -100 kJ
2 C ==> 3 A ∆H = -350 kJ
Target:
A ==> 2 E ∆H = ???
Question 5
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 A + B ==> 3 E ∆H = -350 kJ
B + D ==> 2 E ∆H = +100 kJ
Target:
4 A ==> 3 D + B ∆H = ???
Question 6
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 B + D ==> 3 A + 2 C ∆H = -100 kJ
D + B ==> C + E ∆H = -350 kJ
Target:
3 A + D ==> 2 E ∆H = ???
Question Group 3
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Question 7
Given:
3 A + E ==> 2 B ∆H = -200 kJ
2 A + E ==> B + D ∆H = +300 kJ
Target:
A + E ==> 2 D ∆H = ???
Question 8
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 B + E ==> C + D ∆H = -200 kJ
B + 2 E ==> 2 C ∆H = +300 kJ
Target:
2 D ==> 3 B ∆H = ???
Question 9
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
3 C ==> A + 2 D ∆H = -200 kJ
A + C ==> B + D ∆H = +350 kJ
Target:
3 A ==> C + 2 B ∆H = ???
Master Difficulty Level
Question Group 4
Question 10
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
D + C ==> 2 E ∆H = -150 kJ
2 A ==> 2 C + D ∆H = -100 kJ
A + E ==> D ∆H = -200 kJ
Target:
A + 4 C ==> E ∆H = ???
Question 11
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
A + 2 E ==> 3 D + B ∆H = -300 kJ
C + B ==> D + A ∆H = -200 kJ
2 B + D ==> A + 3 D ∆H = -150 kJ
Target:
2 B + 2 E ==> 3 C ∆H = ???
Question 12
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
A + 2 C ==> 3 B + 2 E ∆H = -50 kJ
2 D + B ==> 2 A + C ∆H = -150 kJ
D + 2 B ==> A + C ∆H = -300 kJ
Target:
A + C ==> 2 E ∆H = ???
Question Group 5
Question 13
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 A + E ==> B + 2 C ∆H = -250 kJ
3 A + E ==> 2 B + D ∆H = -100 kJ
2 B + C ==> A + E ∆H = -150 kJ
Target:
2 B + D ==> 3 C ∆H = ???
Question 14
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
B + C ==> 2 D + E ∆H = -200 kJ
C + D ==> 2 A + B ∆H = -100 kJ
A + B ==> 2 D ∆H = -150 kJ
Target:
E ==> D ∆H = ???
Question 15
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
C + D ==> 2 A + E ∆H = -300 kJ
3 B ==> 2 A + D ∆H = -200 kJ
B + E ==> C + D ∆H = -250 kJ
Target:
E ==> B + C ∆H = ???
Question Group 6
Question 16
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
3 A + E ==> 2 C ∆H = +100 kJ
C + 2 D ==> 2 B ∆H = -200 kJ
C + D ==> A + E ∆H = -150 kJ
Target:
2 B + D ==> 2 E ∆H = ???
Question 17
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
2 B ==> C + E ∆H = +300 kJ
D + E ==> 3 A ∆H = -250 kJ
A + B ==> E ∆H = +100 kJ
Target:
C + D ==> A ∆H = ???
Question 18
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
C + 2 D ==> A + E ∆H = +300 kJ
2 A + E ==> B + C ∆H = +50 kJ
A + E ==> C + D ∆H = -250 kJ
Target:
B ==> A ∆H = ???
Wizard Difficulty Level
Question Group 7
Question 19
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given
2 WO2(s) + O2(g) ==> 2 WO3(s) DH = -506 kJ
2 W(s) + 3 O2(g) ==> 2 WO3(s) DH = -1686 kJ
Target:
2 W(s) + 2 O2(g) ==> 2 WO2(s)
Question 20
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
N2(g) + O2(g) ⟶ 2 NO(g) ΔH = +180.5 kJ
NO(g) + ½ O2(g) ⟶ NO2(g) ΔH = −57.06 kJ
Target
N2(g) + 2 O2(g) ⟶ 2 NO2(g)
Question 21
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
N2H4(l) + O2(g) ==> N2(g) + 2 H2O(g) ∆H = -534.2 kJ
2 H2(g) + O2(g) ==> 2 H2O(g) ∆H = -483.6 kJ
Target:
N2(g) + 2 H2(g) ==> N2H4(l)
Question Group 8
Question 22
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given
H2(g) + F2(g) ==> 2 HF(g) ∆H = -537kJ
C(s) + 2 F2(g) ==> CF4(g) ∆H = -680kJ
2 C(s) + 2 H2(g) ==> C2H4(g) ∆H = 52.3kJ
Target:
C2H4(g) + 6 F2(g) ==> 2 CF4(g) + 4 HF(g)
Question 23
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
C2H2(g) + 5/2 O2(g) ==> 2 CO2(g) + H2O(l) ∆H = -1229.5 kJ
C(s) + O2(g) ==> CO2(g) ∆H = -393.5 kJ
H2(g) + ½ O2(g) ==> H2O(l) ∆H = -285.8 kJ
Target:
2 C(s) + H2(g) ==> C2H2(g)
Question 24
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given
H2(g) + ½ O2(g) → H2O(g) ΔH = −286 kJ
C2H4(g) + 3 O2(g) → 2 CO2(g) + 2 H2O(g) ΔH = −1411 kJ
C2H6(g) + 3/2 O2(g) → 2 CO2(g) + 3 H2O(g) ΔH = −1560 kJ
Target
C2H4(g) + H2(g) → C2H6(g)
Question Group 9
Question 25
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given
2 H2(g) + O2(g) → 2 H2O(l) ∆H = -571.6 kJ
N2O5(g) + H2O(l) →2 HNO3(l) ∆H = -73.7 kJ
½ N2(g) + 3/2 O2(g) + ½ H2(g) → HNO3(l) ∆H = -174.1 kJ
Target:
N2(g) + 5/2 O2(g) → N2O5(g)
Question 26
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given
2 Mg(s) + O2(g) → 2MgO(s) ∆H= -1203.6 kJ
Mg(OH)2(s) → MgO(s) + H2O(l) ∆H= +37.1 kJ
2 H2(g) + O2(g) → 2 H2O(l) ∆H= -571.7 kJ
Target:
Mg(s) + O2(g) + H2(g) → Mg(OH)2(s)
Question 27
Step 1: Manipulate (reverse, multiply by a factor) and add the given equations to produce the target equation.
Step 2: Now use given ∆H values and the manipulations you have made to determine the ∆H for the target reaction.
Given:
C(s) + O2(g) → CO2(g) ΔH = -393.5 kJ/mol
H2(g) + 1/2 O2(g) → H2O(I) ΔH = -285.8 kJ/mol
4 C(s) + 5 H2(g) → C4H10(g) ΔH = -125.7 kJ/mol
Target:
C4H10(g) + 13/2 O2(g) → 4 CO2(g) + 5 H2O(l)