Use the table to answer the question.

Question

Reaction Bonds Present Energy of Bonds Broken and Formed (kJ/mol)
C + O2→CO2
O=O

2 C=O

499

1478

N2+O2→2NO
N≡N

O=O

2 N=O

946

499

1214

S+O2→SO2
O=O

2 S=O

499

1044

2CO+O2→2CO2
2 C≡O

O=O

4 C=O

2148

499

2956

Which reaction is endothermic?

(1 point)
Responses

C + O2→CO2
C plus O sub 2 rightarrow C O sub 2

S+O2→SO2
S plus O sub 2 rightarrow S O sub 2

2CO+O2→2CO2
2 C O plus O sub 2 rightarrow 2 C O sub 2

N2+O2→2NO
N sub 2 plus O sub 2 rightarrow 2 N O
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Answer 1

To determine which reaction is endothermic, we need to compare the total energy of the bonds broken to the total energy of the bonds formed. A reaction is considered endothermic if the energy required to break the bonds is greater than the energy released from forming the bonds.

Let's analyze each reaction using the provided bond energies:

1. C + O2 → CO2

   • Bonds broken: 1 O=O (499 kJ/mol)
   • Bonds formed: 2 C=O (2 * 499 = 998 kJ/mol)
   • Energy change = Bonds broken - Bonds formed = 499 - 998 = -499 kJ/mol (exothermic)

2. N2 + O2 → 2NO

   • Bonds broken: 1 N≡N (946 kJ/mol), 1 O=O (499 kJ/mol) = 1445 kJ/mol
   • Bonds formed: 2 N=O (2 * 1214 = 2428 kJ/mol)
   • Energy change = 1445 - 2428 = -983 kJ/mol (exothermic)

3. S + O2 → SO2

   • Bonds broken: 1 O=O (499 kJ/mol)
   • Bonds formed: 2 S=O (2 * 522 = 1044 kJ/mol)
   • Energy change = 499 - 1044 = -545 kJ/mol (exothermic)

4. 2CO + O2 → 2CO2

   • Bonds broken: 2 C≡O (2 * 1072 = 2144 kJ/mol), 1 O=O (499 kJ/mol) = 2643 kJ/mol
   • Bonds formed: 4 C=O (4* 499 = 1996 kJ/mol)
   • Energy change = 2643 - 1996 = 647 kJ/mol (endothermic)

From the analysis, the reaction that is endothermic is:

2CO + O2 → 2CO2.