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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 96a

The commercial production of nitric acid involves the following chemical reactions:
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)
2 NO(g) + O2(g) → 2 NO2(g)
3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)
(a) Which of these reactions are redox reactions?

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1
Identify the oxidation states of each element in the reactants and products for each reaction.
For the first reaction: 4 NH_3(g) + 5 O_2(g) → 4 NO(g) + 6 H_2O(g), determine the change in oxidation states for nitrogen and oxygen.
For the second reaction: 2 NO(g) + O_2(g) → 2 NO_2(g), determine the change in oxidation states for nitrogen and oxygen.
For the third reaction: 3 NO_2(g) + H_2O(l) → 2 HNO_3(aq) + NO(g), determine the change in oxidation states for nitrogen.
Identify which reactions involve a change in oxidation states, indicating they are redox reactions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Redox Reactions

Redox reactions, or reduction-oxidation reactions, involve the transfer of electrons between substances. In these reactions, one species is oxidized (loses electrons) while another is reduced (gains electrons). Identifying redox reactions requires analyzing changes in oxidation states of the elements involved.
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Oxidation States

Oxidation states (or oxidation numbers) are assigned to atoms in a compound to indicate their degree of oxidation or reduction. The oxidation state helps in determining which atoms are oxidized and which are reduced in a reaction. For example, in the reaction of ammonia with oxygen, nitrogen in NH3 has an oxidation state of -3, which changes to +2 in NO.
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Balancing Chemical Reactions

Balancing chemical reactions is essential to ensure that the number of atoms of each element is conserved throughout the reaction. This involves adjusting coefficients in front of the reactants and products. In redox reactions, balancing also includes ensuring that the total charge is the same on both sides of the equation, which is crucial for identifying the electron transfer.
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