igneous electrolysis is a chemical phenomenon in which a ionic compound any (salt or base, for example), after undergoing the fusion process (change from solid state to state liquid), is subjected to an external electrical current, which leads to the production of two new substances chemical.
When the salt undergoes the fusion process, it undergoes the so-called dissociation ionic, in which it releases a cation and an anion, as in the equation represented below:
XY(s) → X+(1) + Y-(1)
After fusion, when electrical current passes through this medium, the released ions are discharged, as described below.
the anion undergoes oxidation, losing electrons and forming a simple substance, as represented in the equation below:
Y-(1) → Y2 + 2 and
In this process, 2 mol of electrons are released, because 2 mol of anion Y are needed- to form the molecular Y (usually with atomicity 2, Y2). So, your equation can be written as follows:
2 Y-(1) → Y2 + 2 and
the cation undergoes reduction, gaining electrons and forming a simple (metallic) substance, according to the equation below:
X+(1) + and → X(s)
Since the number of electrons in the oxidation must equal the number of electrons in the reduction, we must multiply the above equation by 2, which results in:
2 X+(1) + 2 and → 2 X(s)
The global equation that represents the igneous electrolysis is built from the sum of the fusion equations, oxidation and reduction, eliminating all the items that are repeated in the reactant of one equation and in the product of the other.
Fusion: 2 XY(s) → 2X+(1) + 2Y-(1)
The fusion equation was multiplied by 2 to equal the amount of ions with respect to the oxidation and reduction equations.
Fusion: 2 XY(s) → 2X+(1) + 2Y-(1)
Oxidation: 2 Y-(1) → Y2 + 2 and
Reduction: 2X+(1) + 2 and → 2 X(s)
Global of electrolysis: 2 XY(s) → Y2 + 2 X(s)
See the step by step igneous electrolysis with some examples:
1st Example: Igneous electrolysis of sodium chloride (NaCl)
1st step: Melting sodium chloride by heating the salt.
NaCl(s) → In+(1) + Cl-(1)
2nd stage: Oxidation of the chloride cation (Cl-).
Cl-(1) → Cl2(g) + 2 and
Note that 2 moles of electrons are released, because 2 moles of chloride anion are needed to form molecular chlorine (Cl2). In this sense, the equation can be written:
2 Cl-(1) → Cl2(g) + 2 and
3rd stage: Reduction of sodium cation (Na+).
At+(1) + and → In(s)
Since the number of electrons in the oxidation must equal the number of electrons in the reduction, we must multiply the above equation by 2, which results in:
2 In+(1) + 2 and → 2 In(s)
4th stage: Rewrite of the fusion equation.
As the number of cation and anion has changed, we must multiply the equation obtained in the 1st step by 2.
2 NaCl(s) → 2 In+(1) + 2 Cl-(1)
5th stage: Assembly of the global equation of the igneous electrolysis.
2 NaCl(s) → 2 In+(1) + 2 Cl-(1)
2 Cl-(1) → Cl2(g) + 2 and
2 In+(1) + 2 and → 2 In(s)
To assemble this global equation, just eliminate the item that appears in the reagent of one step and the product of another, as in the case of Na+, Cl- and electrons. So, the global equation will be:
2 NaCl(s) → Cl2(g) + 2 In(s)
2nd Example: Igneous Electrolysis of Aluminum Bromide (AlBr3)
1st step: Sodium chloride fusion from salt heating.
AlBr3(s) → Al+3(1) + 3Br-(1)
As in the salt formula, there are three bromine (Br) atoms, so 3 moles of the bromide anion (Br) are released-).
2nd stage: Bromide cation oxidation (Br-).
3Br-(1) → br2(1) + 3 and
In this process, 2 moles of electrons are released, because 2 moles of bromide anion are needed to form molecular bromine (Br2). So, to equal the number of moles of bromine, we must use the coefficient 3/2 for the compound Br2:
3Br-(1) → 3/2 Br2(1) + 3 and
3rd stage: Reduction of aluminum cation (Al+3).
Al+3(1) + 3 and → Al(s)
Since the number of electrons in the oxidation must equal the number of electrons in the reduction, we must multiply the above equation by 2, resulting in:
2 Al+3(1) + 6 and → 2 Al(s)
4th stage: Bromide equation correction.
As in the aluminum equation, six electrons are used, so in the bromide equation, there must also be six electrons. To do this, we must multiply the equation by 2, which results in:
6 Br-(1) → 3 Br2(1) + 6 and
5th stage: Assembly of the global igneous electrolysis equation.
2 AlBr3(s) → 2 Al+3(1) + 6 Br-(1)
6 Br-(1) → 3 Br2(1) + 6 and
2 Al+3(1) + 6 and → 2 Al(s)
To assemble this global equation, just eliminate the item that appears in the reagent of one step and the product of another, as in the case of Al+3, br- and electrons. So, the global equation will be:
2 AlBr3(s) → 3Br2(1) + 2 Al(s)
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/quimica/o-que-e-eletrolise-ignea.htm
