Understanding Redox Reactions: Balancing Multiple Reductions and Oxidations

In summary, when balancing the reaction CdS + HNO3 (dil) → Cd(NO3)2 + NO + S + H2O, it is important to consider the oxidation numbers of each atom. In this case, both Cd and N are reduced, with Cd going from +5 to +1 and N going from +5 to +2. It is possible for more than one atom to be reduced or oxidized, but in such cases, there would be two separate processes happening. In order for a redox reaction to occur, both reduction and oxidation must be taking place simultaneously.
  • #1
hiturtle
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I am supposed to balance the following reaction:
CdS + HNO3 (dil) → Cd(NO3)2 + NO + S + H2O

After writing out all the oxidation numbers for each atom, I found that Cd and N are both reduced (Cd5+ → Cd 1+ and N5+ → N2+).

I am wondering how to approach this problem. Is it possible to have 2 atoms reduced? Is this what the dilute acid does?
 
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  • #2
Show how you calculated oxidation numbers for Cd and S.

Yes, it may happen that more than one atom gets reduced or oxidized, but in such situations it usually means there are two separate, parallel processes going on - and they can be described by two reaction equations. However, for the redox reaction to proceed you need BOTH reduction and oxidation to be taking place at the same time. So if you have found only elements that are being reduced, there is for sure something wrong.
 

Related to Understanding Redox Reactions: Balancing Multiple Reductions and Oxidations

1. How do you identify a redox reaction?

A redox reaction involves the transfer of electrons between atoms. You can identify a redox reaction by looking for changes in oxidation numbers of the elements involved in the reaction.

2. What is the purpose of balancing a redox reaction?

The purpose of balancing a redox reaction is to ensure that the number of electrons lost by the reducing agent is equal to the number of electrons gained by the oxidizing agent. This maintains the overall charge balance in the reaction.

3. What is the step-by-step process for balancing a redox reaction?

The steps for balancing a redox reaction are:
1. Write the unbalanced equation, and identify the reducing and oxidizing agents.
2. Determine the oxidation numbers of each element in the reactants and products.
3. Write half-reactions for the oxidation and reduction processes.
4. Balance the atoms in each half-reaction, starting with the elements other than oxygen and hydrogen.
5. Balance the oxygen atoms by adding water molecules to the side that lacks oxygen.
6. Balance the hydrogen atoms by adding hydrogen ions to the side that lacks hydrogen.
7. Balance the charge by adding electrons to the side that is more positively charged.
8. Multiply each half-reaction by a factor to ensure that the number of electrons lost in the oxidation half-reaction is equal to the number of electrons gained in the reduction half-reaction.
9. Add the balanced half-reactions together.
10. Check that the atoms, charges, and oxidation numbers are balanced.

4. What is the difference between an oxidation and a reduction reaction?

Oxidation involves the loss of electrons, while reduction involves the gain of electrons. In an oxidation reaction, the oxidation number of an element increases, while in a reduction reaction, the oxidation number decreases.

5. What are some common methods for balancing redox reactions?

Some common methods for balancing redox reactions include the half-reaction method, the oxidation number change method, and the ion-electron method. The half-reaction method is the most commonly used method and involves balancing the oxidation and reduction half-reactions separately before combining them. The oxidation number change method involves using the change in oxidation numbers of the elements to balance the reaction. The ion-electron method involves balancing the number of electrons lost and gained in the reaction to maintain charge balance.

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