Question

Write an equation for the ionization of hydrogen bromide, a molecular substance and a strong acid, in water.

Short answer

The equation for the ionization of hydrogen bromide in water is: \( HBr_{(aq)} + H_2O_{(l)} \rightarrow H_3O^+_{(aq)} + Br^-_{(aq)} \).

Step-by-step solution

Identify the Chemical Species

Understand that hydrogen bromide (HBr) is a molecular substance and a strong acid. When an acid ionizes in water, it donates a proton (H+) to water, forming hydronium ions (H3O+) or leaving behind the conjugate base, in this case, bromide ions (Br-).

Write the Reactants

Begin the equation with the reactants. For the ionization of hydrogen bromide, the reactants are hydrogen bromide (HBr) and water (H2O).

Write the Products

Incorporate the products that result from the ionization. The products are hydronium ions (H3O+) and bromide ions (Br-).

Combine the Reactants and Products

Formulate the complete ionization reaction by combining the reactants and products into a balanced chemical equation. Ensure that the number of atoms of each element is the same on both sides of the equation.

Add the State Symbols

To fully describe the reaction, indicate the physical state of each component; hydrogen bromide and water are both in aqueous solution (aq), as are the ions produced.

Key concepts

Strong Acid in Water

When we talk about acids, particularly those used in a chemistry context, a strong acid is one that completely ionizes in water. This means that when a strong acid is added to water, it releases all of its hydrogen ions into the solution, forming hydronium ions. This is a characteristic feature of strong acids like hydrogen bromide (HBr), which distinguishes them from weak acids that only partially ionize. In an aqueous solution,

the presence of hydronium ions is a clear indicator of acidity, and the higher their concentration, the more acidic the solution becomes. This complete ionization is also what makes strong acids great for various chemical reactions where a swift and complete exchange of ions is beneficial.

Chemical Equations

A chemical equation is a symbolic representation of a chemical reaction. It uses chemical formulas to depict the substances involved in the reaction, known as reactants, and the substances produced, known as products. Writing a chemical equation involves several steps: identifying reactants and products, writing their chemical formulas, and then balancing the equation to ensure the conservation of mass—meaning there are an equal number of each type of atom on both sides of the equation.

An equation must also include the physical states of the reactants and products using state symbols such as (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solution. Especially for reactions involving acids and bases, these state symbols are key in understanding the context of the reaction.

Acid Ionization

The term acid ionization refers to the process by which an acid releases hydrogen ions (H+) into an aqueous solution. Depending on the strength of the acid, this process can be complete or partial. With strong acids like hydrogen bromide (HBr), ionization is complete, meaning that each molecule of acid in water dissociates into its constituent ions.

For hydrogen bromide, the equation for this chemical process looks as follows:
\[\text{HBr}_{(aq)} + \text{H}_2\text{O}_{(l)} \rightarrow \text{H}_3\text{O}^+_{(aq)} + \text{Br}^-_{(aq)}\].
This balanced equation indicates that for every molecule of HBr, one hydronium ion and one bromide ion are produced in the solution.

Hydronium Ions

The hydronium ion, represented by the chemical formula \(\text{H}_3\text{O}^+\), plays a critical role in the chemistry of acids. These positively charged ions are formed when hydrogen ions produced by an acid combine with water molecules. It is the hydronium ion, rather than the hydrogen ion itself, that is responsible for the acidic properties of solutions.

The concentration of hydronium ions determines the pH level of the solution, with a higher concentration correlating to a lower pH value, implying stronger acidity. The presence of hydronium ions is a direct result of the acid ionization process, and their study is vital in understanding acid-base chemistry, neutralization reactions, and the behaviour of acids in water.