Figure 2 shows the displayed equation for the complete combustion of propane. Figure 2
Η Η Η
30=CEO + 4H-0-H
H-C-C-C-H + 50=0
| |
H Η Η
The table below shows bond energies.
Bond
Bond energy in kJ/mol
C-C
347
C-H
413
O=0
495
C=0
799
O-H
467
Calculate the overall energy change in kJ/mol for the reaction.

answer; protein;

i do not get it   at all

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.