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Conductivity and concentrations
Chimica

Conductivity and concentrations

To determine the relation between current intensity and concentration of a strong electrolyte solution.

Elettrochimica
conductivity; concentration; strong electrolytes

Cosa imparano gli studenti

La scienza alla base di questo esperimento

Substances that dissociate into ions are called electrolytes. Acids, bases and salts are electrolytes, and their aqueous solutions conduct an electric current. Sodium chloride as a crystal does not conduct, but dissolved in water its Na+ and Cl− ions allow current to flow.

Attrezzatura utilizzata

  • Digital multimeter — 2275.10
  • DC power supply
  • 1 × Connecting wire, red — 2522.03-04
  • 1 × Connecting wire, black — 2522.04-08
  • 2 × Crocodile clips — 2531.52
  • 4 × Copper electrodes — 4716.21
  • 2 × Test cell covers — 4718.10

Sostanze chimiche e reagenti

  • Sodium chloride solutions of different concentrations
  • Acqua distillata

Note sulla sicurezza

  • Be careful when using the power supply and conductive solutions: risk of electric shock.

Domande per gli studenti

  • Which solution conducts more current?
  • Why?

Cosa aspettarsi

<p>0 A current is measured testing distilled water because distilled water does not conduct electricity.</p><p>Current increases according to the concentration because of the increasing amount of ions present in the solution. A higher value of current is measured every time the solution is replaced with a more concentrated one.</p><p>As concentration increases a greenish colour appears (due to formation of copper ions in solution) and some bubbles may appear (due to the formation of chlorine gas) at the electrodes.</p><p>At the cathode (–), some formation of hydrogen occurs because of the reduction of water. At the anode (+), some formation of chlorine occurs because of the oxidation of chloride ions.</p>

Smaltimento

Dispose of the solutions into the waste container or into the sink.

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