Strong electrolyte vs. Weak electrolytes: What's the Difference?

Key Difference

Strong electrolytes ionize completely in water and are a good conductor of electricity while weak electrolytes ionize partially in water and are a poor conductor of electricity.

Comparison Chart

Strong Electrolytes Weak Electrolytes
Definition Strong electrolytes ionize completely in solutions Weak electrolytes ionize partially in solutions.
Strength Ionization Ionization
Example Perchloric acid, Bromic acid, Triflic acid, potassium hydroxide etc Carbonic acid, phosphoric acid, ammonia etc
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What are strong electrolytes?

An electrolyte is a substance in an aqueous solution which allows electricity to pass through it and decomposes into ions upon conductance. A Strong electrolyte is a substance which ionizes completely and dissociates in aqueous solution when an electric current passes through it. Strong electrolytes are an excellent conductor of electricity. Previously, the strong electrolyte was considered a chemical which was present in aqueous solution and conduct electricity. With a better understanding of the properties of ions in solution, its definition was replaced by the present one. Concentrated solutions of strong electrolyte have lower vapor pressure than that of pure water at the same temperature. Strong electrolytes produce a greater voltage in galvanic cells. Strong electrolytes are strong acids, strong bases and soluble ionic salts that are not weak acid or weak base. The hydroxides of group 1 (which are alkali metal) and group 2 (which are alkaline earth metals) are strong bases and therefore strong electrolytes. Most salts are strong electrolytes.  Examples of strong acids are perchloric acid, hydriodic acid, hydrobromic acid, hydrochloric acid, sulfuric acid, nitric acid, chloric acid, perbromic acid, bromic acid, periodic acid, triflic acid and magic acid. Examples of strong bass are lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, calcium hydroxide, sodium amide, sodium hydride and barium hydroxide. Examples of strong salts are sodium chloride, potassium nitrate, sodium acetate and magnesium chloride.

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What are weak electrolytes?

A weak electrolyte is an electrolyte which does not ionize in aqueous solution. The solution will contain both ions and molecules of the electrolyte. Most acids are weak electrolytes except for a few ones. Water and acetic acid are weak electrolytes. Dissolution of a substance in water is not a determining factor of its strength as an electrolyte. It’s mean dissolution and dissociation are not the same phenomena. For example, an acetic acid which is an acid found in vinegar is highly soluble in water. However, most of the acetic acid leftovers intact as its original state rather than its ionized state which is ethanoate. An equilibrium reaction acts a significant role in this. When acetic acid is dissolved in water, it ionizes into hydronium ions and ethanoate, but the equilibrium position is to the left. It means when ethanoate and hydronium ions are formed; they quickly return to the acetic acid and water:

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CH3COOH + H2O ⇆ CH3COO + H3O+

The little amount of ethanoate makes acetic acid a weak electrolyte rather than a strong electrolyte.

Strong electrolyte vs. Weak electrolytes

  • Weak electrolytes ionize partially about 1% to 10% in water.
  • Strong electrolytes ionize completely 100% in water.
  • Strong electrolytes dissociate completely at moderate concentrations.
  • Weak electrolytes do not dissociate completely at moderate concentrations.
  • The conductance of strong electrolytes increases with increasing the dilution but to at some extent.
  • The conductance of weak electrolytes increases very quickly upon dilution, especially in the infinite dilution.
  • Strong electrolytes have strong interionic interaction at moderate concentrations.
  • Weak electrolytes do not have strong interionic interaction even at higher amounts.

Explanatory Video

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