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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 9

What kind of reaction is the 'water-splitting' reaction? H2O(l)¡H2(g) + ½ O2(g) (a) an acid-base reaction (b) a metathesis reaction (c) a redox reaction (d) a precipitation reaction

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Identify the type of reaction by analyzing the reactants and products.
Recognize that the reaction involves the decomposition of water into hydrogen and oxygen gases.
Understand that in this reaction, water (H2O) is split into hydrogen (H2) and oxygen (O2) molecules.
Note that the oxidation states of elements change during the reaction: hydrogen goes from +1 in H2O to 0 in H2, and oxygen goes from -2 in H2O to 0 in O2.
Conclude that the change in oxidation states indicates that this is a redox (reduction-oxidation) reaction.

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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). The water-splitting reaction demonstrates this as water (H2O) is split into hydrogen gas (H2) and oxygen gas (O2), with oxygen being oxidized and hydrogen being reduced.
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Oxidation States

Oxidation states are a way to keep track of electron transfer in redox reactions. Each atom in a molecule is assigned an oxidation state based on its electron count relative to its elemental form. In the water-splitting reaction, the oxidation state of oxygen increases from -2 in H2O to 0 in O2, indicating that it has been oxidized, while hydrogen's oxidation state decreases from +1 to 0, indicating reduction.
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Electrolysis

Electrolysis is a process that uses electrical energy to drive a non-spontaneous chemical reaction, such as the water-splitting reaction. In this context, an electric current is applied to water, causing it to decompose into hydrogen and oxygen gases. This process is fundamental in various applications, including hydrogen production for fuel cells and energy storage.
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