A common method for producing a gaseous hydride is to treat a salt containing the anion of the volatile hydride with a strong acid. (a) Write an equation for each of the following examples: ( 1 ) the production of HF from \(\mathrm{CaF}_{2} ;\) (2) the production of \(\mathrm{HCl}\) from \(\mathrm{NaCl} ;\) (3) the production of \(\mathrm{H}_{2} \mathrm{~S}\) from FeS. (b) In some cases, even as weak an acid as water can be used for this preparation if the anion of the salt has a sufficiently strong attraction for protons. An example is the production of \(\mathrm{PH}_{3}\) from \(\mathrm{Ca}_{3} \mathrm{P}_{2}\) and water. Write the equation for this reaction. (c) By analogy, predict the products and write the equation for the reaction of \(\mathrm{Al}_{4} \mathrm{C}_{3}\) with water.

Reaction equations are essential for representing chemical reactions by showing reactants and products and their proportions. In the exercise provided, various volatile hydrides are produced by reacting salts with strong acids. Reaction equations help visualize and understand these transformations.

For example, the production of hydrogen fluoride (HF) from calcium fluoride (CaF₂) involves a reaction with sulfuric acid (H₂SO₄). The balanced reaction equation is:
\[ \text{CaF}_2 + \text{H}_2 \text{SO}_4 \rightarrow 2 \text{HF} + \text{CaSO}_4 \]

Similarly, the reactions for producing hydrogen chloride (HCl) and hydrogen sulfide (H₂S) are represented by the following equations:
\[ \text{NaCl} + \text{H}_2 \text{SO}_4 \rightarrow \text{HCl} + \text{NaHSO}_4 \]

\[ \text{FeS} + 2 \text{HCl} \rightarrow \text{H}_2 \text{S} + \text{FeCl}_2 \]

These equations provide a clear and concise depiction of the chemical changes taking place.

Volatile hydrides are a category of chemical compounds that contain hydrogen and are volatile, meaning they can easily vaporize. These compounds are often generated by treating salts with strong acids. They can be gases like hydrogen fluoride (HF), hydrogen chloride (HCl), and hydrogen sulfide (H₂S).

For instance, when calcium fluoride (CaF₂) is treated with sulfuric acid (H₂SO₄), the volatile hydride HF is produced:
\[ \text{CaF}_2 + \text{H}_2 \text{SO}_4 \rightarrow 2 \text{HF} + \text{CaSO}_4 \]

The same process applies for the production of HCl from sodium chloride (NaCl) and H₂S from iron(II) sulfide (FeS). These reactions are characterized by their ability to release volatile compounds as gases, making them crucial in various industrial processes.

• HF is important in glass etching and metal processing.
• HCl is widely used in cleaning, metal refining, and laboratory synthesis.
• H₂S, despite its toxicity, is essential in the synthesis of sulfur-containing compounds.

Understanding how to produce and handle volatile hydrides is key for their practical applications.

Strong acids are substances that completely dissociate in water, producing a high concentration of hydrogen ions (H⁺). This property makes them highly reactive and essential in producing volatile hydrides. Examples of strong acids used in the given exercise include sulfuric acid (H₂SO₄) and hydrochloric acid (HCl).

In these reactions, strong acids donate protons to the anions of salts, forming gaseous hydrides and other by-products. For example:
\[ \text{FeS} + 2 \text{HCl} \rightarrow \text{H}_2 \text{S} + \text{FeCl}_2 \]

Here, HCl donates protons to FeS, producing hydrogen sulfide (H₂S). Strong acids play a crucial role in achieving complete ionization, making the reactions efficient and predictable.

Additionally, water can sometimes act as a weak acid in reactions where the anion has a strong attraction for protons, as seen in the production of phosphine (PH₃) from calcium phosphide (Ca₃P₂) and water:
\[ \text{Ca}_3 \text{P}_2 + 6 \text{H}_2 \text{O} \rightarrow 2 \text{PH}_3 + 3 \text{Ca(OH)}_2 \]

This reaction demonstrates how even a weak acid can facilitate the formation of volatile hydrides under certain conditions.