Chemistry - Exo or Endo

Exothermic and Endothermic

Endothermic

Exothermic

Heat exits the reaction. The surrounding temperature goes up

Heat exits the reaction. The temperature outside goes down

Energy Profiles

Breaking bonds involves putting energy into the reaction

Wen bonds are made energy is released

Reaction Energy Diagram shows the energy at the start of the reaction and at the end

Reaction Pathway along with the activation energy is plotted between the reactants and products

Energy Bond Calculations

Bonds Broken-Bonds Made = Energy Change

Cells and Batteries

In Non-rechargeable cells and batteries, the chemical reactions stop when one of the reactants has been used up. E.g Alkaline batteries

In rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied. Forcing the reaction the other way, therefore the electrons

Hydrogen Fuel Cells

At the Anode (positive), the Hydrogen oxides and produces Hydrogen ions. The electrons move along the circuit

At the Cathode (negative), the Oxygen reduces and gains the electrons creating the oxygen ions

The Hydrogen ions and Oxygen ions form an ionic bond to make water

4H+ + O2+4e-