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Electrolytic solutions

Electrolyte solution is a solution that generally contains ions, atoms or molecules that have lost or gained electrons, and is electrically conductive, there are two types of electrolytes:

  • Strong electrolytes: solutes that dissociate completely in the solvent giving solutions of high electrical conductivity (such as strong acids and bases).

  • Weak electrolytes: solutes that partially dissociate in the solvent resulting in solutions of low electrical conductivity (such as weak acids and bases).

Electrolytic solution can be obtained by dissolving in water:

  • an ionic solid NaCl(s) → Na+(aq) + Cl-(aq)

  • a polar liquid HNO3(l) → H+(aq) + NO3-(aq)

  • a polar gas HCl(g) → H+(aq) + Cl-(aq)

Polar liquids and gases are composed of polar molecules that will dissociate as ions in water. https://youtu.be/D1CfxNvrGkA?si=-p2MC48jYdmjZbNP

Coefficient dissociation α

The dissociation coefficient measures the degree to which a substance dissociates into its constituent ions when in solution, and is expressed as

Noting that α is a dimensionless value that varies between 0 and 1. According to the dissociation coefficient α, electrolytes are divided into two categories: weak electrolytes and strong electrolytes.

  • When α=1, dissociation is total. In this case, the electrolyte is considered strong. This is the case for salts such as NaCl, KCl, CaCl2, strong acids HCl, H2SO4, and strong bases KOH.

  • When 0<α<1 , dissociation is partial, and the solution contains both ions and molecules of the solute. In this case, the electrolyte is considered weak. This is the case for weak acids CH3-COOH and weak bases NH4.

  • When α=0 , there is no dissociation and the solution is non-electrolytic. This is the case for solutions of urea, glucose, and sucrose.

Coefficient ionization i

The ionization coefficient i of a solution is defined as the ratio between the number of particles and the total initial number of molecules introduced into the solvent. In general, the ionization cefficient is expressed as follows:

  • υ is the total number of particles resulting from the dissociation.

  • α is the dissociation coefficient.

  • The ionization coefficient i equals υ for complete dissociation, and it equals 1 for no dissociation.