Define:
(a) Photochemical reaction
(b) Electrochemical reaction.
Give one example in each case.
Define:
(a) Photochemical reaction
(b) Electrochemical reaction.
Give one example in each case.
(a) The photochemical reaction, a chemical reaction initiated by the absorption of energy in the form of light. The consequence of molecules' absorbing light is the creation of transient excited states whose chemical and physical properties differ greatly from the original molecules.
For example
- 2AgCl --> 2Ag+Cl in the presence of sunlight. The silver Chloride turns grey.
- Photosynthesis: plants use solar energy to convert carbon dioxide and water into glucose and oxygen.
- Bioluminescence: e.g. In fireflies, an enzyme in the abdomen catalyzes a reaction that produced light.
(b) An electrochemical reaction is a process in which electrons flow between a solid electrode and substance, such as an electrolyte. This flow triggers an electric current through the electrodes, causing the reaction to liberate or absorb heat.
Under different conditions, other types of reactions create an electric current flow. For example, two electrodes in contact with each other result in a reduction and oxidation (redox) reaction, causing a change in the oxidation numbers of all atoms that are part of the reaction.
Electrochemical Cells: In an electrochemical process, electrons flow from one chemical substance to another, driven by an oxidation-reduction (redox) reaction. A redox reaction occurs when electrons are transferred from a substance that is oxidized to one that is being reduced.
(a) The photochemical reaction, a chemical reaction initiated by the absorption of energy in the form of light. The consequence of molecules' absorbing light is the creation of transient excited states whose chemical and physical properties differ greatly from the original molecules.
For example
- 2AgCl --> 2Ag+Cl in the presence of sunlight. The silver Chloride turns grey.
- Photosynthesis: plants use solar energy to convert carbon dioxide and water into glucose and oxygen.
- Bioluminescence: e.g. In fireflies, an enzyme in the abdomen catalyzes a reaction that produced light.
(b) An electrochemical reaction is a process in which electrons flow between a solid electrode and substance, such as an electrolyte. This flow triggers an electric current through the electrodes, causing the reaction to liberate or absorb heat.
Under different conditions, other types of reactions create an electric current flow. For example, two electrodes in contact with each other result in a reduction and oxidation (redox) reaction, causing a change in the oxidation numbers of all atoms that are part of the reaction.
Electrochemical Cells: In an electrochemical process, electrons flow from one chemical substance to another, driven by an oxidation-reduction (redox) reaction. A redox reaction occurs when electrons are transferred from a substance that is oxidized to one that is being reduced.
