Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot?

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Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot?

 

Electrolytes and Non-electrolytes

    1. Chemical substances can be classified into electrolytes and non-electrolytes.
  1. Electrolytes are substances that can conduct electricity either in the molten state or in an aqueous solution and undergo chemical changes.
  2. Non-electrolytes are substances that cannot conduct electricity either in the molten state or in an aqueous solution.
  3. Conductors are substances that can conduct electricity in the solid or molten state but are not chemically changed. Therefore, conductors are not electrolytes.
  4. Figure illustrates the particles in an electrolyte and a non-electrolyte.
    Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot 1
  5. In general,
    (a) examples of electrolytes are acids, alkalis, salt solutions or molten salts. All these are ionic substances.
    (b) examples of non-electrolytes are covalent substances which do not contain ions.
  6. Ionic compounds do not conduct electricity in the solid state because the ions are held in a lattice and do not move freely. However, when they are melted or dissolved in water, they can conduct electricity. This is because the ions are free to move in the molten state or aqueous solution. For example, solid lead(II) iodide does not conduct electricity while molten lead(II) iodide does.
    Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot 2
  7. Hydrogen chloride, HCl and ammonia, NH3 are covalent compounds. They exist as molecules in organic solvents. Hence, they do not conduct electricity in an organic solvent such as methylbenzene. However, solutions of hydrogen chloride and ammonia in water conduct electricity. This is because they exist as free mobile ions in water.

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Electrolytes and Non-electrolytes Experiment

Aim: To classify substances into electrolytes and non-electrolytes.
Materials: Solid lead(II) bromide, acetamide, naphthalene, sodium hydroxide solution, glucose solution and copper(II) sulphate solution.
Apparatus: Batteries, bulb, switch, connecting wires with crocodile clips, carbon electrodes with holders, crucible,
100 cm3 beaker, Bunsen burner, tripod stand and pipe-clay triangle.
Procedure:

A. For molten substances

  1. Two-thirds of a crucible is filled with solid lead(II) bromide, PbBr2.
  2. The apparatus is set up as shown in Figure.Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot 3
  3. The solid lead(II) bromide is heated until it is completely molten.
  4. The switch is turned on. The changes to the bulb and electrodes are observed.
  5. Steps 1 to 4 are repeated by replacing the solid lead(II) bromide with acetamide, CH3CONH2 and naphthalene, C10H8 respectively.

B. For aqueous solutions

  1. A beaker is filled with sodium hydroxide, NaOH solution until it is half full.
  2. The apparatus is set up as shown in Figure.
    Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot 4
  3. The switch is turned on. The changes to the bulb and electrodes are observed.
  4. Steps 1 to 3 are repeated by replacing the sodium hydroxide solution with glucose, C6H12O6 solution and copper(II) sulphate, CuSO4 solution respectively.

Observations:

SubstanceObservation
Molten lead(ll) bromideThe bulb lights up. A brown gas is released at one of the electrodes.
Molten acetamideThe bulb does not light up. No change at the electrodes
Molten naphthaleneThe bulb does not light up. No change at the electrodes.
Sodium hydroxide solutionThe bulb lights up. Effervescence occurs at both electrodes.
Glucose solutionThe bulb does not light up. No change at the electrodes.
Copper(ll) sulphate solutionThe bulb lights up. Effervescence occurs at one of the electrodes whereas a brown solid is deposited on the other electrode.

Discussion:

  1. Molten lead(II) bromide, sodium hydroxide solution and copper(II) sulphate solution can conduct electricity. This is because they contain free mobile ions which can carry electric current.
    Why is an electrolyte able to conduct electricity while a Nonelectrolyte Cannot 5
  2. The changes at the electrodes show that these substances are decomposed when electricity is passed through them.
  3. Molten acetamide, molten naphthalene and glucose solution cannot conduct electricity. This is because they do not contain ions, but are made up of molecules which cannot carry an electric current.

Conclusion:
Molten lead(II) bromide, sodium hydroxide solution and copper(II) sulphate solution are electrolytes whereas molten acetamide, molten naphthalene and glucose solution are non-electrolytes.

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