Electrochemistry of Metals Summary

Electrochemistry Overview

• Study of electricity in chemical oxidation and reduction (redox) reactions.

• Activity series: ranks metals based on their reactivity.

• Example: Zinc (Zn) is more reactive than Copper (Cu).

• Reactions can be studied using voltmeters to measure potential difference between metals.

Key Reactions

• Dissolving zinc in hydrochloric acid:
  Zn(s) + 2H^+(aq) \rightarrow Zn^{2+}(aq) + H_2(g)

• Non-reactivity of copper in hydrochloric acid:
  Cu(s) + 2 H^+(aq) \rightarrow ext{No reaction}

• Example reaction indicating metal activity:
  2 Ag^+(aq) + Cu(s) \rightarrow Cu^{2+}(aq) + 2 Ag(s)

Redox Reactions

• Definition:

• Oxidation: loss of electrons, reduction: gain of electrons.

• Example reaction breakdown:

• Cu^{2+}(aq) + Zn(s) \rightarrow Cu(s) + Zn^{2+}(aq)

• Oxidation state changes:

  • Zn oxidized from 0 to +2 (loses 2 electrons).

  • Cu reduced from +2 to 0 (gains 2 electrons).

• Half-reactions representation:

• Reduction: Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)

• Oxidation: Zn(s) \rightarrow Zn^{2+}(aq) + 2e^-

Electrochemical Cell Components

• Consists of two half-cells connected by a wire.

• Each metal in its ion solution (e.g., copper ions for copper).

• Salt bridge: maintains charge balance by providing ions; does not participate in reaction.

• Voltmeter measures the potential difference between the two metals.

Potential Measurements

• Varies with different metal pairs; indicates driving force of reaction.

• Positive potential: spontaneous reaction; negative potential: nonspontaneous reaction.

Safety Precautions

• Metals generally not hazardous; ionic solutions can be toxic.

• Wash hands after lab; dispose of metal ion solutions properly.

Materials Needed

• Wire pieces: copper, zinc, nickel, aluminum.

• Plastic well plate.

• 5-10 mL of 0.10 M solutions of Cu2+, Zn2+, Ni2+, Al3+ ions.

• Steel wool.

• Voltmeter with alligator clips.