Question

Although the \(\mathrm{ClO}_{4}^{-}\)and \(\mathrm{IO}_{4}^{-}\)ions have been known for a long time, \(\mathrm{BrO}_{4}^{-}\)was not synthesized until 1965 . The ion was synthesized by oxidizing the bromate ion with xenon difluoride, producing xenon, hydrofluoric acid, and the perbromate ion. (a) Write the balanced equation for this reaction. (b) What are the oxidation states of Br in the Br-containing species in this reaction?

Short answer

(a) The balanced equation for this reaction is: \[\mathrm{BrO}_{3}^{-} + \mathrm{XeF}_{2} \rightarrow \mathrm{BrO}_{4}^{-} + \mathrm{Xe} + 2\mathrm{HF}\] (b) The oxidation states of Br in the Br-containing species are: \[\mathrm{BrO}_{3}^{-} : +5\] \[\mathrm{BrO}_{4}^{-} : +7\]

Step-by-step solution

Identify reactants and products

The reaction involves the following reactants and products: - Reactants: Bromate ion (\(\mathrm{BrO}_{3}^{-}\)) and xenon difluoride (\(\mathrm{XeF}_{2}\)) - Products: Perbromate ion (\(\mathrm{BrO}_{4}^{-}\)), xenon gas (Xe), and hydrofluoric acid (\(\mathrm{HF}\))

Write the unbalanced equation

Now that we have identified the reactants and products, we can write the unbalanced equation for the reaction: \[\mathrm{BrO}_{3}^{-} + \mathrm{XeF}_{2} \rightarrow \mathrm{BrO}_{4}^{-} + \mathrm{Xe} + \mathrm{HF}\]

Balance the equation

To balance the equation, we need to make sure that the number of atoms of each element is conserved. We can break down the balance process as follows: - There are the same number of Br atoms on each side (1 atom), so we can leave it as it is. - There is 1 xenon atom on both sides; no changes needed. - However, there are 2 fluorine atoms on the left side but only 1 on the right side. To balance the fluorine atoms, we need to place a coefficient of 2 in front of the HF. Now we have the balanced equation: \[\mathrm{BrO}_{3}^{-} + \mathrm{XeF}_{2} \rightarrow \mathrm{BrO}_{4}^{-} + \mathrm{Xe} + 2\mathrm{HF}\]

Determine the oxidation states of Br-containing species

In order to determine the oxidation states of the Br-containing species, we will analyze the oxidation state of Br in each of the species: - \(\mathrm{BrO}_{3}^{-}\): Since O generally has an oxidation state of -2 and there are 3 O atoms, the sum of the oxygen oxidation states is -6. Since the charge of the ion is -1, Br's oxidation state must be +5. - \(\mathrm{BrO}_{4}^{-}\): Similarly, O has an oxidation state of -2 and there are 4 O atoms giving a sum of -8. With an ion charge of -1, the oxidation state of Br is determined to be +7. To summarize: (a) The balanced equation is: \[\mathrm{BrO}_{3}^{-} + \mathrm{XeF}_{2} \rightarrow \mathrm{BrO}_{4}^{-} + \mathrm{Xe} + 2\mathrm{HF}\] (b) The oxidation states of Br in the Br-containing species are: \[\mathrm{BrO}_{3}^{-} : +5\] \[\mathrm{BrO}_{4}^{-} : +7\]

Key concepts

Oxidation States

Understanding oxidation states is crucial when studying chemical reactions, especially in the context of redox reactions. Oxidation states, or oxidation numbers, help chemists keep track of electron transfer by assigning a hypothetical charge to an atom if it were to exist as an ion. In essence, these numbers describe the degree of oxidation of an atom in a chemical compound.

For instance, in the given exercise, we determined the oxidation states of bromine (Br) in the reactants and products. This was done by considering the general rule that oxygen has an oxidation state of -2. In the bromate ion (\(\mathrm{BrO}_3^-\)), with three oxygen atoms contributing a total of -6 to the oxidation state and the ion itself carrying a charge of -1, we can calculate the oxidation state of bromine to be +5. Correspondingly, in the perbromate ion (\(\mathrm{BrO}_4^-\)), four oxygen atoms lead to an overall -8, while the ion carries -1 charge, giving bromine an oxidation state of +7.

Why Are Oxidation States Important?

Determining oxidation states helps in identifying which element is oxidized and which is reduced during the reaction. Oxidation involves an increase in oxidation state (loss of electrons), while reduction involves a decrease (gain of electrons). This is elegantly showcased in the formation of \(\mathrm{BrO}_4^-\) where bromine's oxidation state increases, implying that it is being oxidized.

• Oxidation states facilitate balancing redox reactions.
• They are essential for understanding electron transfer in a reaction.
• Knowing oxidation states helps in predicting the properties and reactivity of elements in different compounds.

Chemical Reaction

A chemical reaction is a process where reactants transform into products through breaking and forming of chemical bonds. This process often involves energy changes and is subject to the conservation of mass and charge.

Balancing chemical equations is a fundamental skill in chemistry, ensuring that the same number of atoms for each element is present on both sides of the reaction equation. In the provided problem, we needed to balance the equation for the oxidation of bromate ion by xenon difluoride. The equation was balanced when we determined that two molecules of hydrofluoric acid were produced, thus conserving mass and charge.

Key Aspects of Chemical Reactions:

• Reactants are substances initially present before a reaction takes place.
• Products are substances formed as a result of the reaction.
• Chemical reactions can be classified into types such as synthesis, decomposition, single-replacement, double-replacement, and combustion.
• Reactions often require energy, such as heat, light, or electricity, to proceed.

Chemical reactions are represented by balanced chemical equations, which serve as a shorthand for describing the changes that occur. The exercise showcases a balanced chemical reaction, integral to understanding chemical processes.

Inorganic Chemistry

Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds, which include metals, minerals, and organometallic compounds. It is a diverse field that covers a wide range of substances excluding many carbon-based compounds, which are the focus of organic chemistry.

The synthesis of the perbromate ion is a classic task in inorganic chemistry that involves understanding and applying principles such as oxidation states and balancing chemical equations. Inorganic reactions often form the basis for materials science and are involved in various industries including catalysis, materials synthesis, and environmental chemistry.

Inorganic chemistry also studies coordination compounds, crystal structure, and various physical properties associated with inorganic materials. The synthesis of \(\mathrm{BrO}_4^-\) not only deepened the knowledge of bromine chemistry but also contributed to the wider field by providing insights into the behavior of halogen compounds in different oxidation states.