Saved Bookmarks
| 1. |
important points on bond enthalpy for quick revision. if possible write in notebook! |
| Answer» ENERGY. Quantifying the energy represented by the bonds in DIFFERENT molecules is an important part of understanding the overall energy implications of a reaction. In this article, we'll explore two different concepts that help describe that energy: enthalpy of reaction and bond enthalpy.Enthalpy of reactionDuring chemical reactions, the bonds between atoms may break, reform or both to either absorb or release energy. The result is a change to the POTENTIAL energy of the system. The heat absorbed or released from a system under constant pressure is known as enthalpy, and the change in enthalpy that results from a chemical reaction is the enthalpy of reaction. The enthalpy of reaction is often written as \Delta\text H_{\text{rxn}}ΔH rxn delta, start text, H, end text, start subscript, start text, r, x, n, end text, end subscript.To better understand enthalpy of reaction, let's consider the hydrogenation of propene, \text{C}_3 \text{H}_6C 3 H 6 start text, C, end text, start subscript, 3, end subscript, start text, H, end text, start subscript, 6, end subscript, to form propane, \text{C}_3 \text{H}_8C 3 H 8 start text, C, end text, start subscript, 3, end subscript, start text, H, end text, start subscript, 8, end subscript. In this reaction, propene gas reacts with hydrogen gas, \text H_2(G)H 2 (g)start text, H, end text, start subscript, 2, end subscript, left parenthesis, g, right parenthesis, to form propane gas:~~~~~~~\text{C}_3 \text{H}_6(g)~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~ \text H_2(g) ~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text{C}_3 \text H_8 (g) | |