Problem 194 - Introductory Chemistry Atoms First

Question

Give an example of a covalent compound that, upon dissolving in water, yields ions. Write a reaction to show this transformation and classify the starting compound.

Step-by-Step Solution

Answer

An example of a covalent compound that dissolves in water and produces ions is hydrogen chloride (HCl). The dissolution of hydrogen chloride in water can be represented by the following balanced reaction: \[ HCl_{(g)} + H_2O_{(l)} \rightarrow H_3O^+_{(aq)} + Cl^-_{(aq)} \] The starting compound, hydrogen chloride (HCl), can be classified as a simple covalent binary compound and as an acid (hydrochloric acid) when dissolved in water.

Step 1: Identify a covalent compound that dissolves in water and produces ions

A good example of such a compound is hydrogen chloride (HCl), which is a covalent compound since hydrogen and chlorine are both nonmetal elements. When hydrogen chloride dissolves in water, it ionizes to produce hydrogen ions (H+) and chloride ions (Cl-). Now that we have identified hydrogen chloride (HCl) as our compound, we can write the balanced reaction for its dissolution in water.

Step 2: Write the balanced reaction for the dissolution of the chosen compound in water

When hydrogen chloride (HCl) dissolves in water, the reaction can be represented as: \[ HCl_{(g)} + H_2O_{(l)} \rightarrow H_3O^+_{(aq)} + Cl^-_{(aq)} \] Finally, we will classify our starting compound - hydrogen chloride (HCl).

Step 3: Classify the starting compound

Hydrogen chloride (HCl) is categorized as a simple covalent binary compound. It consists of two nonmetal elements, hydrogen and chlorine, bound together by sharing a pair of electrons. Additionally, it is also an acid, known as hydrochloric acid, when dissolved in water.

Key Concepts

Hydrogen Chloride

Hydrogen chloride (HCl) is a fascinating example of a covalent compound with unique properties. It consists of hydrogen and chlorine, both of which are nonmetal elements linked together by a covalent bond. This means they share a pair of electrons, allowing them to achieve greater stability.
When hydrogen chloride is in its gaseous form, it appears as colorless gas. But, its real magic is revealed when it interacts with water.

• Upon dissolving in water, HCl transforms into hydrochloric acid, which is a vital industrial and laboratory reagent.
• HCl is also significant in everyday life as it's part of our stomach acid, aiding in digestion.

Understanding hydrogen chloride helps us appreciate chemical reactions that involve the movement of electrons and the conversion of covalent compounds into ionic forms upon dissolution.

Ionization in Water

Ionization in water is a crucial concept for understanding how certain covalent compounds can produce ions. In the case of hydrogen chloride, when it's dissolved in water, it undergoes ionization. This process involves hydrogen chloride splitting into hydrogen ions ( H^+ ) and chloride ions ( Cl^- ).
The reaction can be depicted as:

• Initially, the hydrogen chloride reacts with water molecules ( H_2O_{(l)} ), resulting in the formation of hydronium ions ( H_3O^+ ) and chloride ions ( Cl^- ).
• This transformation not only modifies the state of the compound from covalent to ionic, but it also turns the solution acidic due to the presence of hydronium ions.

The breakdown of covalent bonds during ionization in water illustrates the dynamic nature of chemical interactions, facilitating key transformations in various chemical processes.

Binary Compounds

Binary compounds are essential components of chemistry, formed from two different types of elements. Hydrogen chloride (HCl), which is a type of binary compound, consists of hydrogen and chlorine.

• Binary compounds can be either ionic or covalent. HCl is a covalent binary compound because it involves electron sharing between nonmetals.
• Another example of a binary compound is sodium chloride, which is ionic because it involves the transfer of electrons between a metal and a nonmetal.

Understanding binary compounds like HCl helps in grasping the diversity and potential of chemical interactions. Moreover, classification into binary covalent or ionic is based on how these two different elements bond, highlighting the importance of electron-sharing or electron-transfer mechanisms in determining the nature of substances. By studying binary compounds, we unveil how elements combine to form a vast array of chemical species.