Огляд компонент гальванічного елементу

On this page, we are going to introduce voltaic cells and go over their important components.

What is a voltaic cell?

A voltaic cell is an electrochemical cell that utilizes a reduction-oxidation reaction to produce electrical energy. Voltaic cells are also called galvanic cells.

Voltaic cells have several important components that I will list here before I explain more in depth later:

• electrode: a strip of metal where the reaction takes place

• anode: an electrode where oxidation occurs

• cathode: an electrode where reduction occurs

• salt bridge: chamber of electrolytes needed to complete the circuit in a voltaic cell

• half-cells: separate compartments of oxidation and reduction reactions. When two half-cells are linked by a wire and salt bridge, an electrochemical cell is formed

• external circuit: used to conduct flow of electrons between electrodes

• load: part of circuit that utilizes the flow of electrons to perform some function (i.e. a light bulb)

In redox reaction, electrons are transferred from one species to the other. If the reaction is spontaneous, this transfer releases a source of energy. This energy produced by the reaction can be harnessed to do useful work, but it must be split into its two separate half reactions in order to do so. These are the oxidation and reduction reactions. These reactions are put into two separate containers that contains a wire used to drive the electrons from one container to the other.

Let's consider a reaction of solid copper ($Cu_{(s)}$) in a silver nitrate solution ($AgNO_{3(s)}$) to explain this process. Let's start by writing the balanced reaction.

$2Ag^{+}_{(aq)} + Cu_{(s)} \Leftrightarrow Cu^{2+}_{(aq)} + 2Ag_{(s)}$

This reaction releases energy, but unfortunately that energy is lost to heat. However, by splitting the reaction into its oxidation and reduction halves, the energy can be harnessed. Let's take a look at how we would do that:

This image shows two different electrodes immersed in solutions of the same metal, or two half-cells that are connected by a wire and a salt bridge. The ions in solution are called electrolytes and can conduct electricity through ionic conduction. The metal atoms on the electrodes can react with the ion solutions in two different ways.

On the left, we have a copper anode submerged in a $CuSO_{4}$ solution. The copper atoms on the surface may lose 2 electrons and enter the solution as a $Cu^{2+}$ ion. This means that the metal ions are oxidized.

Oxidation will always occur in the half-cell with the anode. We can tell that copper is the anode, because its oxidation state increases from 0 to +2.

On the right, we have a silver cathode emerged in a $AgNO_{3}$ solution. The $Ag^{+}$ ions from the solution may collide with the electrode and gain an electron. The metal ions are converted to metal atoms, meaning the ions are reduced.

Reduction will always occur in the half-cell with the anode. We can tell the silver is the cathode, because its oxidation state decreases from +1 to 0.

The salt bridge we see connecting the two half-cells is a vital component to a voltaic cell that allows the electrons to flow freely from one cell to the other by keeping the solutions electrically neutral. Salt bridges are tubes that are filled with electrolyte solutions. In the image, we see $KNO_{3}$ being used, but $KCl$ can also be found in a salt bridge.

The electrons will always flow from the anode to the cathode, or from the oxidation half to the reduction half.

Just to make sure we have our cathode and anode properties in order, let's go over it one more time.

• Anode: oxidation (metal loses electrons)

• Cathode: reduction (metal gains electrons)

If you also need a trick to think of what it means to be "oxidized" or "reduced" think of the phrase "OIL RIG"

OIL = Oxidation Is Loss (of $e^{-}$)

RIG = Reduction Is Gain ( of $e^{-}$)

At this point you should have an understanding of the components of a voltaic diagram, so now you can move on to learn about active vs. inert electrodes. You can also click the link to learn about how a electric current moves through voltaic cells. And lastly here you will find some typical voltaic cell diagrams!

(Video) Galvanic Cells (Voltaic Cells)

by Tyler DeWitt

In this video, Tyler DeWitt explains voltaic cells. It's a very comprehensive explanation. You'll learn about each component of a voltaic cell. He'll also illustrate the flow of electrons and ions. After watching this video, you'll have a strong understanding of voltaic cells.