Reklama

Electrolysis

Find out more, as the current passes through the solution, in which have mobile ions. Liquid conductor, in which mobile charge carriers are ions, called electrolytes. Let in a bath filled with a solution of sulfuric acid in water. Dissociation of molecules of sulfuric acid takes place in accordance with the equation

Immerse in a bath of a platinum plate and connect them through the ammeter to the battery (rice. 19.2). These plates are called electrodes.

The electrode, connected with the positive pole of the battery, call the anode, the electrode, connected to the negative pole, — cathode. If you close the chain key, it is in the electrolyte between the electrodes an electric field.

Under the action of this field forces the hydrogen ions H+ will rush to the cathode, ions and acid balance SO-4 — to the anode. When he reached the cathode, ions H+ attached to one of the free electrons of the plate and are transformed into neutral hydrogen atoms. Connecting in pairs, these atoms form molecules of hydrogen gas, which Deposit on the cathode.

It turns out, in the mentioned case, in addition to ions SO-4 in the electrolyte there are other negative ions, because the molecules of water itself in small quantities is also dissotsiiruyut:

Ions HE- (the hydroxyl) easily give your excess electron, and the ions SO-4 hold their electrons more firmly. Therefore, at the anode, where suitable negative ions, HE discharged ions-, and ions SO-4 remain in solution. At the discharge ions HE- water is formed and neutral molecules of oxygen gas, which is at the anode.

Denoting the absolute value of electron charge by the letter e, all these processes can be written as follows:

So, from the solution leaving the constituent parts of water molecules, as part of the acid molecules remain in solution. This means, as of current flow the amount of water in the solution decreases, and the concentration of the solution increases. That's why the process described is sometimes referred to as decomposition of water electric.

From described above seen, the passage of electric current through the electrolyte is accompanied by the transformation of substances, t. e. the current in the electrolyte produces chemical action. Passing through the electric electrolytes, accompanied by chemical transformations of a substance and release it on the electrodes, is called electrolysis. The vessel with the electrodes, in which the electrolyte, call electrolytic bath.

Positive ions in solution is called cations (because during electrolysis they go to the cathode), and negative ions anions. Recall, what cations are hydrogen ions and metals.

In the example, the substance is excreted at both electrodes. As we will see in the next section, this is not always the case. The release of a substance at both electrodes occurs at inactive anode, which is not soluble in the electrolyte. In our example, the plates do not react with the electrolyte. In the technique for such electrolysis are more likely to use coal or graphite electrodes.

The current in the electrolyte obeys Ohm's law, t. e. varies in direct proportion to the voltage. When heated, the electrolytes decreases the viscosity and increases the mobility of ions. In addition, upon heating of the electrolyte increases the degree of dissociation of the molecules of the dissolved substance, t. e. increases the number of current carriers in the electrolyte. This means, the resistance of the electrolyte decreases when heated.

Reklama