Question

. Name four strong acids. For each of these, write the equation showing the acid dissociating in water.

Short answer

The four strong acids are Hydrochloric Acid (HCl), Sulfuric Acid (H2SO4), Nitric Acid (HNO3), and Hydroiodic Acid (HI). Their dissociation equations in water are as follows: 1. \( \text{HCl} \, (aq) \rightarrow \text{H}^+(aq) + \text{Cl}^-(aq) \) 2. \( \text{H}_2\text{SO}_4 \, (aq) \rightarrow 2 \text{H}^+(aq) + \text{SO}_4^{2-}(aq) \) 3. \( \text{HNO}_3 \, (aq) \rightarrow \text{H}^+(aq) + \text{NO}_3^-(aq) \) 4. \( \text{HI} \, (aq) \rightarrow \text{H}^+(aq) + \text{I}^-(aq) \)

Step-by-step solution

Identifying four strong acids

The four strong acids we will focus on are Hydrochloric Acid (HCl), Sulfuric Acid (H2SO4), Nitric Acid (HNO3), and Hydroiodic Acid (HI). These acids are considered strong because they ionize completely in water, yielding a high concentration of hydrogen ions.

Writing the dissociation equation for Hydrochloric Acid (HCl)

In water, hydrochloric acid dissociates completely to produce hydrogen ions (H+) and chloride ions (Cl-). The equation for this dissociation is: \[ \text{HCl} \, (aq) \rightarrow \text{H}^+(aq) + \text{Cl}^-(aq) \]

Writing the dissociation equation for Sulfuric Acid (H2SO4)

In water, sulfuric acid dissociates completely to produce hydrogen ions (H+) and sulfate ions (SO4^2-). The equation for this dissociation is: \[ \text{H}_2\text{SO}_4 \, (aq) \rightarrow 2 \text{H}^+(aq) + \text{SO}_4^{2-}(aq) \]

Writing the dissociation equation for Nitric Acid (HNO3)

In water, nitric acid dissociates completely to produce hydrogen ions (H+) and nitrate ions (NO3-). The equation for this dissociation is: \[ \text{HNO}_3 \, (aq) \rightarrow \text{H}^+(aq) + \text{NO}_3^-(aq) \]

Writing the dissociation equation for Hydroiodic Acid (HI)

In water, hydroiodic acid dissociates completely to produce hydrogen ions (H+) and iodide ions (I-). The equation for this dissociation is: \[ \text{HI} \, (aq) \rightarrow \text{H}^+(aq) + \text{I}^-(aq) \] In conclusion, we have identified four strong acids and written their respective dissociation equations in water.

Key concepts

Acid Dissociation in Water

Understanding how acids dissociate in water is crucial to grasp the nature of acidity in solutions. When an acid is dissolved in water, it releases hydrogen ions (\text{H}^+) into the solution. The measure of an acid's strength lies in its ability to dissociate completely. Strong acids, such as hydrochloric acid (\text{HCl}), sulfuric acid (\text{H}_2\text{SO}_4), nitric acid (\text{HNO}_3), and hydroiodic acid (\text{HI}), are almost completely ionized in solution, which means they release a large number of hydrogen ions. This complete dissociation is key to their high reactivity.

The process of dissociation for strong acids can be summarized by the general equation:\[ \text{HA} \rightarrow \text{H}^+ + \text{A}^- \]where \text{HA} represents the acid and \text{A}^- stands for the conjugate base of the acid. The extent of dissociation for strong acids is so significant that the reverse reaction, where the hydrogen ions and the conjugate base recombine to form the undissociated acid, is negligible.

Hydrochloric Acid (HCl)

Hydrochloric acid (\text{HCl}) is a prime example of a strong acid and is widely used in various industrial processes. When dissolved in water, \text{HCl} ionizes completely, forming hydrogen ions and chloride ions as expressed in the dissociation equation shown below:\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]This reaction illustrates the one-to-one ratio in which the hydrogen ions and chloride ions are produced. Since \text{HCl} dissociates completely, it marks the solution as highly acidic and capable of conducting electricity due to the presence of these free ions.

Sulfuric Acid (H2SO4)

Sulfuric acid (\text{H}_2\text{SO}_4), often used in battery acid and industrial cleaners, is another potent acid that shows a two-step dissociation process in water due to its two hydrogen atoms. The initial dissociation can be represented as:\[ \text{H}_2\text{SO}_4 \rightarrow \text{H}^+ + \text{HSO}_4^- \] The \text{HSO}_4^- can further dissociate, as indicated in the second step:\[ \text{HSO}_4^- \rightarrow \text{H}^+ + \text{SO}_4^{2-} \]However, it's the first step that completes almost entirely, highlighting \text{H}_2\text{SO}_4 as a strong acid. The abundant production of hydrogen ions quickly lowers the pH of the solution, indicating a high level of acidity. Additionally, sulfuric acid's ability to donate more than one hydrogen ion per molecule makes it a relatively strong acid compared to others.

Nitric Acid (HNO3)

Nitric acid (\text{HNO}_3) is a strong acid with numerous applications, including fertilizer production and metal refining. Its dissociation equation is representative of its complete ionization in water:\[ \text{HNO}_3 \rightarrow \text{H}^+ + \text{NO}_3^- \]Upon dissolution, nitric acid liberates hydrogen ions and nitrate ions, \text{NO}_3^-. This complete ionization makes nitric acid a strong oxidizing agent and lends it the properties necessary for a wide range of chemical reactions, including those used for making explosives such as nitroglycerin. Tyically found in acid rain, nitric acid illustrates the environmental impact strong acids have when released into the atmosphere.

Hydroiodic Acid (HI)

Despite being less commonly encountered than other strong acids, hydroiodic acid (\text{HI}) features a complete dissociation in water, releasing hydrogen ions and iodide ions as expressed in:\[ \text{HI} \rightarrow \text{H}^+ + \text{I}^- \]This behavior is typical of a strong acid, where \text{HI} is fully ionized, providing a high concentration of \text{H}^+ ions which contribute to the high acidity of the solution. While \text{HI} is a gas in its pure form, it exhibits all the properties of a strong acid when dissolved in water, making it a tool in chemical synthesis and an important compound in the realm of organic chemistry.