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

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

C + O2→CO2

Answer 1

To determine which reaction is endothermic, we need to look at the energy values associated with the bonds broken and formed in each reaction. An endothermic reaction occurs when the energy required to break bonds is greater than the energy released from forming new bonds.

Let's analyze each reaction:

1. C + O2 → CO2

   • Energy of bonds broken: O=O (499 kJ)
   • Energy of bonds formed: 2 C=O (1478 kJ)
   • Net energy change = 499 kJ (broken) - 1478 kJ (formed) = -979 kJ (exothermic)

2. N2 + O2 → 2NO

   • Energy of bonds broken: N≡N (946 kJ) + O=O (499 kJ) = 1445 kJ
   • Energy of bonds formed: 2 N=O (1214 kJ)
   • Net energy change = 1445 kJ (broken) - 1214 kJ (formed) = 231 kJ (endothermic)

3. S + O2 → SO2

   • Energy of bonds broken: O=O (499 kJ)
   • Energy of bonds formed: 2 S=O (1044 kJ)
   • Net energy change = 499 kJ (broken) - 1044 kJ (formed) = -545 kJ (exothermic)

4. 2CO + O2 → 2CO2

   • Energy of bonds broken: 2 C≡O (2148 kJ) + O=O (499 kJ) = 2647 kJ
   • Energy of bonds formed: 4 C=O (2956 kJ)
   • Net energy change = 2647 kJ (broken) - 2956 kJ (formed) = -309 kJ (exothermic)

Based on the calculations, the only reaction that is endothermic is:

N2 + O2 → 2NO