Question

What molecule loses a proton to form the hydroxide ion, \(\mathrm{OH}^{-}\)?

Short answer

Water, \( ext{H}_{2} ext{O}\), loses a proton to form \( ext{OH}^{-}\).

Step-by-step solution

Identifying the OH- ion

The hydroxide ion is represented by the chemical formula \( ext{OH}^{-}\), which is a negatively charged ion.

Understanding Proton Loss

When a molecule loses a proton (\( ext{H}^{+}\)), it typically forms another ion or molecule. The hydroxide ion is formed when a neutral molecule loses a proton.

Finding the Neutral Molecule

To form \( ext{OH}^{-}\) from losing a proton, the original molecule must be neutral and contain one hydrogen atom and an OH group. The molecule that fits this description is water, \( ext{H}_{2} ext{O}\).

Reaction Representation

The chemical equation for this process is \( ext{H}_{2} ext{O} \rightarrow ext{OH}^{-} + ext{H}^{+}\). This shows that water can lose a proton to form the hydroxide ion.

Key concepts

Proton Loss

Proton loss is a fundamental concept in chemistry where a molecule loses a hydrogen ion, also known as a proton (\( \mathrm{H}^{+} \)). This process is crucial in many chemical reactions and can lead to the formation of new ions or molecules.
When a molecule undergoes proton loss, it typically becomes charged because the removal of a positively charged proton alters the original charge balance of the molecule.
Proton loss is essential in understanding the behavior of acids and bases. In this context, acids release protons, while bases accept them. For instance, when water loses a proton, it becomes a hydroxide ion, which helps to maintain the balance of ions in aqueous solutions.

Chemical Equation

A chemical equation is a symbolic representation of a chemical reaction. It shows the starting substances (reactants) on the left and the resulting substances (products) on the right.
In the case of hydroxide ion formation, the chemical equation is \( \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{OH}^{-} + \mathrm{H}^{+} \).
This equation illustrates the process of water losing a proton to become a hydroxide ion, \( \mathrm{OH}^{-} \), and a hydrogen ion, \( \mathrm{H}^{+} \).

• The left side of the equation represents the water molecule (reactant).
• The right side represents the hydroxide ion and the proton (products).

Chemical equations like this one help visualize the transformation of molecules during reactions, highlighting the changes in molecular structure and charge.

Neutral Molecule

A neutral molecule is a molecule that has no overall charge. This means that the number of protons (positive charges) is equal to the number of electrons (negative charges) within the molecule.
Water, with the formula \( \mathrm{H}_{2}\mathrm{O} \), is a perfect example of a neutral molecule. It has two hydrogen atoms and one oxygen atom, making up a stable, balanced structure with equal positive and negative charges.

• It remains chemically neutral until it participates in a reaction involving proton transfer.
• Changes from a neutral to a charged state when a proton is either donated or accepted.

Understanding neutral molecules is vital for grasping reactions like proton loss, where the conversion of neutral molecules to ions is central.

Water as a Molecule

Water is one of the most profound and common examples of a chemical compound in which interesting reactions such as proton loss can occur. It consists of two hydrogen atoms covalently bonded to one oxygen atom, composing the neutral molecule \( \mathrm{H}_{2}\mathrm{O} \).

• Its molecular makeup allows it to easily lose a proton, thereby forming a hydroxide ion (\( \mathrm{OH}^{-} \)).
• This is an important reaction in chemistry, exemplifying water's role as a reactant that can change its charge state.

Water's ability to transform into hydroxide ions when losing a proton is fundamental in many biochemical and environmental processes. This ion exchange is crucial for maintaining pH balance in biological systems and supports various chemical reactions in nature.