Question

Write a chemical equation that describes the dissolving of the following substances in water: (a) gaseous hydrogen chloride, \(\mathrm{HCl}\) (b) chlorine gas, \(\mathrm{Cl}_{2}\) (c) solid magnesium nitrate, \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\)

Short answer

The dissolved equations of the substances are as follows: (a) \(\mathrm{HCl}(g)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{H}_{3}\mathrm{O}^{+}(aq) +\mathrm{Cl}^{-}(aq)\); (b) \(\mathrm{Cl}_{2}(g)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{HOCl}(aq)+\mathrm{HCl}(aq)\); (c) \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(s)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{Mg^{2+}}(aq) + 2\mathrm{NO_{3}^-}(aq)\).

Step-by-step solution

Dissolving Hydrogen Chloride In Water

Hydrogen chloride forms hydrochloric acid when dissolved in water. So the equation will be: \(\mathrm{HCl}(g)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{H}_{3}\mathrm{O}^{+}(aq) +\mathrm{Cl}^{-}(aq)\)

Dissolving Chlorine Gas In Water

Dissolving chlorine gas in water forms hypochlorous acid and hydrochloric acid. The equation is: \(\mathrm{Cl}_{2}(g)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{HOCl}(aq)+\mathrm{HCl}(aq)\)

Dissolving Magnesium Nitrate In Water

Magnesium nitrate forms magnesium ions and nitrate ions when dissolved in water. The equation is \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(s)+\mathrm{H}_{2}\mathrm{O}(l)\rightarrow\mathrm{Mg^{2+}}(aq) + 2\mathrm{NO_{3}^-}(aq)\)

Key concepts

Dissolving Substances

Dissolving is a fascinating chemical process, where a substance mixes with a solvent to form a solution. In this context, water is typically the solvent, making it an essential medium in chemical reactions.
Let's break down how various substances dissolve in water and the resulting chemical equations involved.

• Gas to Liquid: When a gaseous substance like hydrogen chloride \(\mathrm{HCl}\) enters water, it forms a new substance. Here, hydrogen chloride forms hydrochloric acid, which dissolves in water relatively easily.
• Solids in Liquid: For solid substances such as magnesium nitrate \(\mathrm{Mg(NO_{3})_{2}}\), these solids break into ions in an aqueous solution. This means they separate into smaller particles, allowing them to mix with the water molecules surrounding them. The magnesium nitrate separates into magnesium ions and nitrate ions.
• Gas Reaction: With gases like chlorine \(\mathrm{Cl}_{2}\), the interaction is more complex, forming new substances, such as hypochlorous acid and hydrochloric acid, upon dissolving in water.

Each of these processes involves breaking and forming of bonds, creating new substances and solutions.

Hydrochloric Acid Formation

When hydrogen chloride gas \(\mathrm{HCl}\) dissolves in water, it initiates the formation of hydrochloric acid, a vital compound in chemistry.
This transformation is key in many industrial applications and laboratory settings, making it crucial for chemists to understand.To conceptualize this process, visualize \(\mathrm{HCl}\) gas molecules entering water and interacting with water molecules. This interaction leads to the creation of hydrochloric acid, represented by the following chemical equation:\[ \mathrm{HCl}(g) + \mathrm{H_2O}(l) \rightarrow \mathrm{H_3O^+}(aq) + \mathrm{Cl^-}(aq) \]
Here are the crucial components of this reaction:

• Hydrogen Ion Formation: The hydrogen atom in \(\mathrm{HCl}\) forms a hydronium ion \(\mathrm{H_3O^+}\), contributing to the acidic nature of the solution.
• Chloride Ion: The chloride ion \(\mathrm{Cl^-}\) remains in the aqueous solution as a counter ion to the hydronium.

Understanding hydrochloric acid formation explains how acids behave in water and their roles in various chemical reactions. Recognizing this helps in predicting reactions in both educational and practical applications.

Ionization in Water

Ionization is an essential process that occurs when substances dissolve in water, producing ions. This concept is crucial for understanding many chemical reactions and properties of solutions.When substances like magnesium nitrate \(\mathrm{Mg(NO_{3})_{2}}\) dissolve in water, they undergo ionization. This means they split into positive and negative ions.
Let's look at how ionization proceeds for magnesium nitrate:\[ \mathrm{Mg(NO_{3})_{2}}(s) + \mathrm{H_2O}(l) \rightarrow \mathrm{Mg^{2+}}(aq) + 2\mathrm{NO_{3}^-}(aq) \]
Key points of ionization:

• Ionic Separation: In this dissolving process, the compound separates into its constituent ions. Magnesium becomes \(\mathrm{Mg^{2+}}\) ions, and the nitrates become \(\mathrm{NO_{3}^-}\) ions in the solution.
• Aqueous State: These ions are surrounded by water molecules and evenly distributed within it, termed being in 'aqueous' form.

Ionization is significant for its role in solutions' conductivity and reactivity. Understanding this means we can predict and explain several behaviors of solutions, like their electrical conductivity and reactions with other substances.