Use the chart below to answer the following question.
Substance
D
G
f
º (kJ/mol)
C
2
H
2
(
g
)
209.0
CO
2
(
g
)
–394.0
H
2
O (
l
)
–237.0
O
2
(
g
)
0.0
Which of the following represents the approximate change in standard free energy per mole for the combustion of C
2
H
2
(
g
)?
–20 kJ/mol
+20 kJ/mol
–100 kJ/mol
–1200 kJ/mol
+1200 kJ/mol