Hess's Law
AP Chemistry · Flashcards · Application
AP CHEMISTRY · FLASHCARDS
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QUESTION
Find the enthalpy change for a reaction if
ΔH
reaction
=
−
150
kJ
\text{ΔH}_{\text{reaction}} = -150 \text{ kJ}
ΔH
reaction
=
−
150
kJ
,
ΔH
1
=
−
100
kJ
\text{ΔH}_1 = -100 \text{ kJ}
ΔH
1
=
−
100
kJ
.
QUESTION
Calculate the total enthalpy:
ΔH
1
=
70
kJ
\text{ΔH}_1 = 70 \text{ kJ}
ΔH
1
=
70
kJ
,
ΔH
2
=
−
30
kJ
\text{ΔH}_2 = -30 \text{ kJ}
ΔH
2
=
−
30
kJ
,
ΔH
3
=
20
kJ
\text{ΔH}_3 = 20 \text{ kJ}
ΔH
3
=
20
kJ
.
QUESTION
Calculate the change in enthalpy if
ΔH
1
=
60
kJ
\text{ΔH}_1 = 60 \text{ kJ}
ΔH
1
=
60
kJ
,
ΔH
2
=
90
kJ
\text{ΔH}_2 = 90 \text{ kJ}
ΔH
2
=
90
kJ
,
ΔH
3
=
−
30
kJ
\text{ΔH}_3 = -30 \text{ kJ}
ΔH
3
=
−
30
kJ
.
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ANSWER
ΔH
reaction
=
120
kJ
\text{ΔH}_{\text{reaction}} = 120 \text{ kJ}
ΔH
reaction
=
120
kJ
. Add all steps:
60
+
90
+
(
−
30
)
=
120
60 + 90 + (-30) = 120
60
+
90
+
(
−
30
)
=
120
kJ.
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