From the reaction given below, write an ionic equation to show which substance is oxidized and reduced.
a. [tex]Na ( s )+ CaCl _2[/tex] (aq)
i. substance oxidized
ii. substance reduced
b. [tex]K ( s )+ AgNO _3( aq )[/tex]
i. substance oxidized
ii. substance reduced
c. [tex]Mg ( s )+ CuSO _4( aq )[/tex]
i. substance oxidized
ii. substance reduced
Balance the equation if necessary.
Answer (2)
The problem involves identifying oxidation and reduction in three chemical reactions and writing the balanced ionic equations. In each reaction, we determine which substance loses electrons (oxidized) and which gains electrons (reduced). The balanced ionic equations show only the species that participate in the redox process.
a) N a is oxidized to N a + , and C a 2 + is reduced to C a . The balanced ionic equation is 2 N a ( s ) + C a 2 + ( a q ) → 2 N a + ( a q ) + C a ( s ) .
b) K is oxidized to K + , and A g + is reduced to A g . The balanced ionic equation is K ( s ) + A g + ( a q ) → K + ( a q ) + A g ( s ) .
c) M g is oxidized to M g 2 + , and C u 2 + is reduced to C u . The balanced ionic equation is M g ( s ) + C u 2 + ( a q ) → M g 2 + ( a q ) + C u ( s ) .
The substances oxidized and reduced are: a) N a , C a 2 + , b) K , A g + , c) M g , C u 2 + .
Explanation
Problem Analysis We will analyze each reaction separately to identify the oxidized and reduced substances and write the balanced ionic equations.
Reaction a - Balanced Equation a) N a ( s ) + C a C l 2 ( a q ) → 2 N a Cl ( a q ) + C a ( s )
Reaction a - Oxidation Numbers Oxidation numbers: N a : 0 → + 1 , C a : + 2 → 0 . Sodium is oxidized, and Calcium is reduced.
Reaction a - Oxidation Half-Reaction Oxidation half-reaction: N a → N a + + e −
Reaction a - Reduction Half-Reaction Reduction half-reaction: C a 2 + + 2 e − → C a
Reaction a - Balanced Ionic Equation Balanced ionic equation: 2 N a ( s ) + C a 2 + ( a q ) → 2 N a + ( a q ) + C a ( s )
Reaction b - Balanced Equation b) K ( s ) + A g N O 3 ( a q ) → K N O 3 ( a q ) + A g ( s )
Reaction b - Oxidation Numbers Oxidation numbers: K : 0 → + 1 , A g : + 1 → 0 . Potassium is oxidized, and Silver is reduced.
Reaction b - Oxidation Half-Reaction Oxidation half-reaction: K → K + + e −
Reaction b - Reduction Half-Reaction Reduction half-reaction: A g + + e − → A g
Reaction b - Balanced Ionic Equation Balanced ionic equation: K ( s ) + A g + ( a q ) → K + ( a q ) + A g ( s )
Reaction c - Balanced Equation c) M g ( s ) + C u S O 4 ( a q ) → M g S O 4 ( a q ) + C u ( s )
Reaction c - Oxidation Numbers Oxidation numbers: M g : 0 → + 2 , C u : + 2 → 0 . Magnesium is oxidized, and Copper is reduced.
Reaction c - Oxidation Half-Reaction Oxidation half-reaction: M g → M g 2 + + 2 e −
Reaction c - Reduction Half-Reaction Reduction half-reaction: C u 2 + + 2 e − → C u
Reaction c - Balanced Ionic Equation Balanced ionic equation: M g ( s ) + C u 2 + ( a q ) → M g 2 + ( a q ) + C u ( s )
Final Answers Final Answers: a) i. Substance oxidized: N a ii. Substance reduced: C a 2 + b) i. Substance oxidized: K ii. Substance reduced: A g + c) i. Substance oxidized: M g ii. Substance reduced: C u 2 +
Examples
Understanding oxidation and reduction is crucial in many real-world applications, such as batteries, corrosion prevention, and industrial chemical processes. For example, in a battery, a metal like zinc is oxidized, releasing electrons that power a device, while another substance is reduced, accepting those electrons. Similarly, understanding these processes helps prevent rust on cars by applying coatings that preferentially oxidize instead of the iron in the car's body.
In these reactions, sodium, potassium, and magnesium are oxidized, while calcium, silver, and copper are reduced. The balanced ionic equations for each reaction show how electrons transfer between these substances. Understanding these redox reactions is key in chemistry.
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