Leaving Cert Chemistry Oxidation & Reduction: Using oxidation numbers, or othe

Using oxidation numbers, or otherwise, balance the following equation - Leaving Cert Chemistry - Question e - 2012

Question e

Using oxidation numbers, or otherwise, balance the following equation. $$\text{Cu} + \text{NO}_3^{-} + \text{H}^{+} \rightarrow \text{Cu}^{2+} + \text{NO}_2 + \text... show full transcript

Worked Solution & Example Answer:Using oxidation numbers, or otherwise, balance the following equation - Leaving Cert Chemistry - Question e - 2012

Step 1

Balance the elements in the reaction

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Answer

First, identify the oxidation states of each element:

In Cu, the oxidation state is 0.
In NO3-, the oxidation state of N is +5.
In H+, the oxidation state of H is +1.
In Cu2+, the oxidation state is +2.
In NO2, the oxidation state of N is +4.

Since copper is oxidized from 0 to +2, this involves the loss of 2 electrons. The nitrogen is reduced from +5 in NO3- to +4 in NO2.

Step 2

Balance the charges

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Answer

In order to balance the charges in the reaction:

On the left side, we have 1 negative charge from NO3- and 4 positive charges from 4 H+. This gives a total charge of +3.
On the right side, Cu2+ contributes +2, and NO2 is neutral, thus leaving us with a charge of +2. To balance the charges, we need to include 2 NO3- on the left side.

Step 3

Final balanced equation

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Answer

After balancing the elements and charges, the balanced equation is:

$\text{Cu} + 2\text{NO}_3^{-} + 4\text{H}^{+} \rightarrow \text{Cu}^{2+} + 2\text{NO}_2 + 2\text{H}_2\text{O}$

Using oxidation numbers, or otherwise, balance the following equation - Leaving Cert Chemistry - Question e - 2012

Worked Solution & Example Answer:Using oxidation numbers, or otherwise, balance the following equation - Leaving Cert Chemistry - Question e - 2012

Balance the elements in the reaction

Balance the charges

Final balanced equation

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