The enthalpy (AH) is +624.7 kJ for the following reaction. How would you classify this reaction? (Explain) SiO2(g) + 3C(s) --> SIC(s) +2CO(g)

A. exothermic: heat is lost by the system
B. endothermic: heat is gained by the system
C. endothermic: heat is lost by the system
D. exothermic: heat is gained by the system

The reaction is classified as endothermic: heat is gained by the system.

Explanation:

A process or reaction in which heat is absorbed is called endothermic reaction.

For example, melting of ice is an endothermic process.

For an endothermic reaction the sign of is positive which means heat is gained by the system.

Here, the given reaction is as follows.

A process or reaction in which heat is released is called exothermic reaction.

For example, combustion reaction, freezing of water etc are exothermic process.

For an exothermic reaction the sign is negative which means heat is lost by the system.

Thus, we can conclude that the reaction is classified as endothermic: heat is gained by the system.

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."