use the information in the table to answer the question
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reaction | bonds present | energy bonds broken and formed (kJ/mol)
C+O2>CO2 | O+O | 498
2 C=O | 1478
N2+O2>2NO | N≡N | 946
O=O | 498
2 N=O | 1214
S+O2>SO2 | O=O | 498
2 S=O | 1044
2CO+O2>SO2| 2 C≡O | 2148
O=O | 498
4 C=O | 2956
which reaction is endo thermic?
A ) N2+O2>2NO
B ) S+O2>SO2
C ) 2CO+O2>2CO2
D ) C+O2>CO2
To determine if a reaction is endothermic, we can look at the energy required to break bonds and compare that to the energy released when new bonds are formed. An endothermic reaction is one in which the energy required to break bonds is greater than the energy released when new bonds form, meaning the reaction absorbs energy from its surroundings.
Let's compare the energies for each reaction given in the table:
A) N2 + O2 > 2NO
Energy required to break bonds: N≡N (946 kJ/mol) + O=O (498 kJ/mol) = 1444 kJ/mol
Energy released forming new bonds: 2 N=O (2 * 607 kJ/mol) = 1214 kJ/mol
Net energy = Energy required - Energy released = 1444 - 1214 = 230 kJ/mol (positive value indicates endothermic)
B) S + O2 > SO2
Energy required to break bonds: O=O (498 kJ/mol)
Energy released forming new bonds: 2 S=O (1044 kJ/mol)
Net energy = Energy required - Energy released = 498 - 1044 = -546 kJ/mol (negative value indicates exothermic)
C) 2CO + O2 > 2CO2
Energy required to break bonds: 2 C=O (2 * 1074 kJ/mol) + O=O (498 kJ/mol) = 2646 kJ/mol
Energy released forming new bonds: 4 C=O (4 * 739 kJ/mol) = 2956 kJ/mol
Net energy = Energy required - Energy released = 2646 - 2956 = -310 kJ/mol (negative value indicates exothermic)
D) C + O2 > CO2
Energy required to break bonds: O=O (498 kJ/mol)
Energy released forming new bonds: 2 C=O (1478 kJ/mol)
Net energy = Energy required - Energy released = 498 - 1478 = -980 kJ/mol (negative value indicates exothermic)
From the calculations above, we can see that:
- Reaction A (N2 + O2 > 2NO) is the only endothermic reaction as it has a positive net energy change.
- Reactions B, C, and D are exothermic as they have negative net energy changes, meaning they release more energy than they absorb.
Therefore, the answer is:
A) N2 + O2 > 2NO