Question

Consider the reactlon of water with \(\mathrm{F}_{2}\) and suggest, in terms of oxidation and reduction, which species are oxidised/reduced.

Short answer

Oxygen is oxidized; fluorine is reduced.

Step-by-step solution

Write the Chemical Reaction

Given the reaction of water with \(\mathrm{F}_2\), we can express it as follows: \[\mathrm{2H_2O + 2F_2 \rightarrow 4HF + O_2}\]

Assign Oxidation Numbers

Assign oxidation numbers to each element in the reactants and products: \(\mathrm{H_2O}\): H = +1, O = -2; \(\mathrm{F_2}\): F = 0; \(\mathrm{HF}\): H = +1, F = -1; \(\mathrm{O_2}\): O = 0.

Identify the Changes in Oxidation Numbers

Observe the changes: Oxygen goes from -2 in \(\mathrm{H_2O}\) to 0 in \(\mathrm{O_2}\); Fluorine goes from 0 in \(\mathrm{F_2}\) to -1 in HF.

Determine the Oxidation Process

Oxygen's oxidation number increases from -2 to 0, indicating that oxygen is oxidized.

Determine the Reduction Process

Fluorine's oxidation number decreases from 0 to -1, indicating that fluorine is reduced.

Key concepts

Oxidation Numbers

Understanding oxidation numbers is crucial for grasping the concept of redox reactions. Oxidation numbers, sometimes known as oxidation states, are theoretical charges assigned to atoms in molecules or ions.Each element in a compound can be assigned a specific oxidation number based on a few rules:

• The oxidation number of an element in its elemental form is always zero. For example, in \(\mathrm{F}_2\), both fluorine atoms have an oxidation number of 0.
• For a monatomic ion, the oxidation number equals the charge of the ion. For example, the oxidation number of \(\mathrm{Cl}^-\) is -1.
• Hydrogen is typically assigned an oxidation number of +1, and oxygen is generally assigned -2 in most compounds.

By assigning these numbers, we can track how they change during a chemical reaction.When the oxidation number of an element increases, the element is oxidized. Conversely, when the oxidation number decreases, the element is reduced.

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances, called products. These reactions follow the law of conservation of mass, meaning that the number of atoms for each element is the same in both the reactants and products.In the given exercise, we observe the reaction between water and fluorine: \[\mathrm{2H_2O + 2F_2 \rightarrow 4HF + O_2}\]. This balanced equation shows the reactants on the left transforming into products on the right. The stoichiometry of the equation shows that two molecules of water react with two molecules of fluorine to produce four molecules of hydrogen fluoride and one molecule of oxygen.Chemical reactions can be categorized into different types, such as synthesis, decomposition, single displacement, and double displacement. However, some reactions, including the one in the exercise, are better characterized as redox reactions. This is because they involve the transfer of electrons between the reactants, changing their oxidation states.

Redox Processes

Redox reactions are a fascinating class of chemical reactions emphasizing electron transfer. The term 'redox' is short for reduction-oxidation, describing the processes happening simultaneously: reduction and oxidation. In any redox reaction, if one element is oxidized (loses electrons), another must be reduced (gains electrons).In the reaction provided in the exercise: \[\mathrm{2H_2O + 2F_2 \rightarrow 4HF + O_2}\], we observe that oxygen is being oxidized and fluorine is being reduced. Oxygen in \(\mathrm{H_2O}\) increases its oxidation number from -2 to 0 as it forms \(\mathrm{O_2}\), indicating a loss of electrons. Meanwhile, fluorine in \(\mathrm{F}_2\) decreases its oxidation number from 0 to -1 in forming hydrogen fluoride \(\mathrm{HF}\), showing a gain of electrons.This mutual gain and loss shows that redox reactions are complementary. As electrons are transferred, one substance is oxidized, and another is reduced. Understanding redox reactions is essential in chemistry as they are a fundamental part of many processes in both nature and industrial applications.