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Two synthesis reactions are shown
CHEMISTRY · Subjective · A Level · Chemistry · Energetics · Energetics
Problem
Two synthesis reactions are shown, each written per mole of product formed. Reaction A:
C
(
s
,
graphite
)
+
1
2
O
2
(
g
)
→
CO
(
g
)
Δ
H
=
−
111
kJ
\text{C}(s,\,\text{graphite})+\tfrac12\,\text{O}_2(g)\rightarrow \text{CO}(g)\qquad \Delta H=-111\;\text{kJ}
C
(
s
,
graphite
)
+
2
1
O
2
(
g
)
→
CO
(
g
)
Δ
H
=
−
111
kJ
Reaction B:
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
g
)
Δ
H
=
−
242
kJ
\text{H}_2(g)+\tfrac12\,\text{O}_2(g)\rightarrow \text{H}_2\text{O}(g)\qquad \Delta H=-242\;\text{kJ}
H
2
(
g
)
+
2
1
O
2
(
g
)
→
H
2
O
(
g
)
Δ
H
=
−
242
kJ
Which reaction is more exothermic per mole of product, and how do you know?
Related theory
Thermodynamics
Types of enthalpy
Endothermic and exothermic reactions
Enthalpy Changes of Reactions
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