Multiple Choice
Which one of the following is an endothermic process?
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8. Thermochemistry
Endothermic & Exothermic Reactions
Multiple Choice
Which of the following chemical equations represents an exothermic reaction at 298 K?
A
6CO_2(g) + 6H_2O(l) ightarrow C_6H_{12}O_6(s) + 6O_2(g) \,\;\(\Delta\) H = +2801\;\(\text{kJ}\)
B
2H_2(g) + O_2(g) ightarrow 2H_2O(l) \,\;\(\Delta\) H = -572\;\(\text{kJ}\)
C
CaCO_3(s) ightarrow CaO(s) + CO_2(g) \,\;\(\Delta\) H = +178\;\(\text{kJ}\)
D
N_2(g) + O_2(g) ightarrow 2NO(g) \,\;\(\Delta\) H = +180\;\(\text{kJ}\)
Verified step by step guidance1
Understand that an exothermic reaction releases heat to the surroundings, which means the enthalpy change (\$\(\Delta\) H\$) for the reaction is negative.
Look at the given chemical equations and their associated enthalpy changes (\$\(\Delta\) H\$ values).
Identify the sign of each \$\(\Delta\) H\$: if it is positive, the reaction is endothermic (absorbs heat); if it is negative, the reaction is exothermic (releases heat).
From the list, find the reaction with a negative \$\(\Delta\) H\$ value, indicating it is exothermic.
Confirm that the reaction with \$\(\Delta\) H = -572\;\(\text{kJ}\)\$ is exothermic, while the others with positive \$\(\Delta\) H\$ values are endothermic.
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