- The reaction is: \(Cu(s) + 2AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2Ag(s)\).
- Copper (\(Cu\)) is oxidized as its oxidation number increases from \(0\) to \(+2\): \(Cu \rightarrow Cu^{2+} + 2e^-\).
- Silver ions (\(Ag^+\)) are reduced as their oxidation number decreases from \(+1\) to \(0\): \(Ag^+ + e^- \rightarrow Ag\).
Explanation
- Formulate and Balance the Chemical Equation
When metallic copper (\(Cu\)) is placed into an aqueous solution of silver nitrate (\(AgNO_3\)), a single-displacement chemical reaction occurs. In this reaction, the more reactive copper metal replaces the silver ions in the solution, forming copper(II) nitrate (\(Cu(NO_3)_2\)) and silver metal (\(Ag\)).
To formulate the unbalanced equation:
\[Cu(s) + AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + Ag(s)\]
To balance this equation, we observe that there are two nitrate groups (\(NO_3^-\)) on the right side, so we need two moles of \(AgNO_3\) on the left. This results in two moles of \(Ag\) being produced on the right.
The balanced symbolic chemical equation is:
\[Cu(s) + 2AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2Ag(s)\]
- Identify the Substance Oxidized
Oxidation involves the loss of electrons and an increase in the oxidation number. In our reaction, metallic copper (\(Cu^0\)) is oxidized to copper(II) ions (\(Cu^{2+}\)).
The oxidation half-reaction is:
\[Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-\]
Justification using Oxidation Numbers (O.N.):
- The oxidation number of elemental copper (\(Cu\)) is \(0\).
- The oxidation number of copper in copper(II) nitrate (\(Cu(NO_3)_2\)) is \(+2\) (since the nitrate ion \(NO_3^-\) has a charge of \(-1\)).
- Since the oxidation number increased from \(0\) to \(+2\), copper is oxidized.
- Identify the Substance Reduced
Reduction involves the gain of electrons and a decrease in the oxidation number. In our reaction, silver ions (\(Ag^+\)) from the silver nitrate solution are reduced to metallic silver (\(Ag^0\)).
The reduction half-reaction is:
\[Ag^+(aq) + e^- \rightarrow Ag(s)\]
Justification using Oxidation Numbers (O.N.):
- The oxidation number of silver in the silver nitrate solution (\(Ag^+\)) is \(+1\).
- The oxidation number of elemental silver (\(Ag\)) is \(0\).
- Since the oxidation number decreased from \(+1\) to \(0\), the silver ion is reduced.
Examples
A practical application of this reaction is in the extraction of silver from its ores or in artistic processes like 'silvering'. By immersing a copper object in a silver-containing solution, you can create a thin, decorative layer of silver on the surface of the copper. This is a classic example of redox chemistry, which is fundamental to understanding corrosion, electroplating, and the operation of batteries. Understanding how metals exchange electrons helps engineers design better materials and power sources.