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Chapter 10: Problem 51

How are oxidation states useful in determining whether a reaction is a redox reaction?

Short Answer

Expert verified
Oxidation states are useful in determining whether a reaction is a redox reaction by comparing the oxidation states of the reactants with those of the products. If there is a change in the oxidation states of one or more elements, the reaction is a redox reaction, involving the transfer of electrons between atoms. In a redox reaction, one species undergoes oxidation (loses electrons), while another undergoes reduction (gains electrons). If the oxidation states remain unchanged, it is not a redox reaction.

Step by step solution

01

Define a redox reaction.

A redox (short for reduction-oxidation) reaction is a chemical reaction where the oxidation state of one or more elements in a compound changes. This happens through two simultaneous processes: oxidation and reduction. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.
02

Understand oxidation states.

Oxidation states are a way of keeping track of the distribution of electrons in a compound. Each element in a compound is assigned an oxidation state that represents its ability to gain or lose electrons. A change in the oxidation state indicates a transfer of electrons between atoms. Oxidation states help us understand the behavior of elements in a chemical reaction, especially when electrons are gained or lost.
03

Determine the change in oxidation states.

To determine whether a reaction is a redox reaction, we need to compare the oxidation states of the reactants with those of the products. If there is a change in the oxidation states of one or more elements, the reaction is a redox reaction. If the oxidation states remain unchanged, it is not a redox reaction.
04

Go through an example.

Let's look at an example to illustrate the application of oxidation states in determining redox reactions. Consider the following reaction: \(H_2 + Cl_2 \rightarrow 2HCl\) First, we assign oxidation states to all the elements in the reactants and products: Reactants: \(H_2\) has an oxidation state of 0 and \(Cl_2\) also has an oxidation state of 0. Products: In \(HCl\), H has an oxidation state of +1 and Cl has an oxidation state of -1. Comparing the oxidation states, we can see that the H atoms have increased from 0 to +1 (loss of electrons), while the Cl atoms have decreased from 0 to -1 (gain of electrons). This change in oxidation states indicates that the reaction is a redox reaction. In summary, oxidation states are useful in determining whether a reaction is a redox reaction or not. If there is a change in the oxidation states of one or more elements in a reaction, it is a redox reaction.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Oxidation States
Oxidation states, also known as oxidation numbers, are critical in the realm of chemistry for keeping track of the electrons within a compound. Think of oxidation states as imaginary charges that atoms would have if the compound was made up of ions. They tell us how many electrons an atom has gained, lost, or shared to become stable.

The rules for assigning oxidation states range from simple (the oxidation state of a pure element is always zero) to more complex (in compounds, the sum of oxidation states must equal the overall charge). For instance, in a water molecule (H_2O), hydrogen has an oxidation state of +1 and oxygen has an oxidation state of -2, and together they balance out to zero. Understanding these numbers is crucial as they're the first step to identifying a redox reaction, where changes in these numbers indicate a shift in electron locations.
Decoding Chemical Reactions
Chemical reactions are the processes by which substances, known as reactants, transform into new substances called products. To visualize it, imagine a dance of atoms, where they break their existing bonds and form new ones.

There are various types of chemical reactions, but redox reactions are unique in that they involve the movement of electrons, changing the oxidation states of the atoms. In our body, food is metabolized through redox reactions for energy. In batteries, redox reactions are harnessed to store and provide power. By tracking oxidation states, chemists can deduce the specifics of these reactions, predict products, and understand the role of different species in the reaction.
The Role of Electron Transfer
Electron transfer is the essence of a redox reaction. It's the 'redox' that makes 'redox' a fun dance of give and take. When an atom loses electrons, we say it has been oxidized; it might as well wave goodbye as its oxidation state increases. On the other hand, gain of electrons means reduction, and here the oxidation state decreases, as if an atom is taking a bow.

This electron exchange is not merely swapping; it is the fundamental process that drives the energy in batteries, fuels combustion engines, and even facilitates the breath of life itself through cellular respiration. Identifying these transfers is key to interacting with the wondrous world of chemistry on a deeper level.
Oxidation and Reduction: Two Sides of the Same Coin
Oxidation and reduction always come in a pair – think of them as the chemical world's dynamic duo. You can't have one without the other because they balance each other out. To put it simply, if one species gives away electrons, another must be there to receive them. Oxidation is characterized by an increase in oxidation state, while reduction sees a decrease.

An easy way to remember this is the mnemonic 'OIL RIG': Oxidation Is Loss, and Reduction Is Gain (of electrons). By examining changes in oxidation states, scientists decipher which atoms are the donors and which are the acceptors in this elegant relay race of electrons. It's this fundamental concept that turns the gears of countless natural and technological processes.

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Most popular questions from this chapter

When assigning an oxidation state to an atom, why do we need to know how many valence electrons are present on a free atom of that element?

A battery is made by connecting strips of lead and palladium and dipping each metal into a solution of its ions \(\left(\mathrm{Pb}^{2+}\right.\) and \(\mathrm{Pd}^{2+}\), respectively). Over time, the mass of the lead strip decreases and the mass of the palladium strip increases. (a) Which metal is the anode? (b) Which metal is the cathode? (c) Write the spontaneous redox reaction going on in this battery.

The spontaneous redox reaction \(\mathrm{Mn}+\mathrm{Cd}^{2+} \rightarrow \mathrm{Mn}^{2+}+\mathrm{Cd}\) takes place in a battery. (a) What is the oxidizing agent? (b) What is the reducing agent? (c) Which metal is the cathode? (d) Which metal is the anode?

What must always be true when you add up all the oxidation states for the atoms in a molecule?

Using the EMF series on page 391, decide which of the following redox reactions is spontaneous. Explain your answer. (a) \(3 \mathrm{Ag}+\mathrm{Au}^{3+} \rightarrow \mathrm{Au}+3 \mathrm{Ag}^{+}\) (b) \(\mathrm{Au}+3 \mathrm{Ag}^{+} \rightarrow 3 \mathrm{Ag}+\mathrm{Au}^{3+}\)
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