Question

A bottle of acid solution is labeled " \(3 \mathrm{M} \mathrm{HNO}_{3}\)." What are the substances that are actually present in the solution? Are any \(\mathrm{HNO}_{3}\) molecules present? Why or why not?

Short answer

In a 3M HNO3 aqueous solution, the substances present are water (H2O), hydrogen ions (H+), and nitrate ions (NO3-). HNO3 is a strong acid that ionizes completely in water, meaning it dissociates into H+ and NO3- ions. As a result, very few, if any, HNO3 molecules actually remain in the solution.

Step-by-step solution

Interpreting the label "3M HNO3"

The label "3M HNO3" refers to a 3 molar solution of nitric acid (HNO3). This means that there are 3 moles of HNO3 per liter of solution.

Identifying the substances in the solution

In an aqueous solution (water being the solvent), HNO3, or nitric acid, is a strong acid that ionizes completely. This means that the HNO3 molecules dissociate into their separate ions when in water. Specifically, the HNO3 molecules ionize to produce hydrogen ions (H+) and nitrate ions (NO3-). So, the substances that are present in the solution are water (H2O), hydrogen ions (H+), and nitrate ions (NO3-).

Presence of HNO3 molecules in the solution

As we mentioned before, HNO3 is a strong acid that ionizes completely in water. This means that when HNO3 is added to water, it separates into H+ and NO3- ions and very few, if any, HNO3 molecules actually remain in the solution. So, in a 3M HNO3 aqueous solution, there are very few HNO3 molecules present, if any.

Conclusion

In the given 3M HNO3 aqueous solution, the substances that are present are water (H2O), hydrogen ions (H+), and nitrate ions (NO3-). Due to the complete ionization of HNO3 in water, very few, if any, HNO3 molecules actually remain in the solution.

Key concepts

Ionization

Ionization is a crucial concept in understanding chemical reactions, especially when it comes to acids in solutions. When a substance ionizes, it splits into its constituent ions. This process happens when certain compounds interact with solvents like water, which is common in most chemical solutions.

For strong acids, such as nitric acid (\(\text{HNO}_3\)), ionization occurs entirely. This means that when \(\text{HNO}_3\) is dissolved in water, it separates completely into hydrogen ions (\(\text{H}^+\)) and nitrate ions (\(\text{NO}_3^-\)).

• Complete Ionization: Complete ionization implies that nearly every molecule of the acid breaks apart into ions. This results in a high concentration of ions in the solution.
• Implications: The complete ionization of nitric acid means that in the solution, hydrogen ions and nitrate ions are the dominant species rather than the whole acid molecule.

Understanding ionization helps explain why certain substances behave strongly in terms of acidity in aqueous solutions. It determines the concentration of ions available in the solution, affecting both its reactivity and pH level.

Nitric Acid

Nitric acid (\(\text{HNO}_3\)) is a common and highly reactive chemical compound. It is classified as a strong acid because it ionizes completely in water, forming \(\text{H}^+\) and \(\text{NO}_3^-\) ions.

• Properties: Nitric acid is a corrosive and highly reactive substance. Due to full ionization, it is known to have powerful oxidizing properties.
• Uses: It is widely used in the manufacture of fertilizers, explosives, and in various industrial processes due to its reactivity.

When dissolved in water to form an aqueous solution, nitric acid exhibits its characteristic behavior due to the release of hydrogen ions. These ions are what impart the acidic properties to the solution, increasing its capability to engage in chemical reactions, including corrosive ones with metals and organic compounds.

Aqueous Solutions

An aqueous solution is a type of chemical solution where water acts as the solvent. In aqueous solutions, the solute, which could be an acid, base, salt, or other chemical, is dissolved in water, resulting in a solution.

• Hydration: When substances dissolve in water, they often interact with water molecules through hydration. This involves the attraction between the solute molecule's ions and water molecules.
• Dissociation: For compounds like nitric acid (\(\text{HNO}_3\)), aqueous solutions enable dissociation, leading to ion formation, which is crucial for conducting electricity.

Understanding aqueous solutions is essential because water is the most common solvent in nature and industry. Many reactions occur in aqueous solutions, where the behavior of substances changes due to interactions with water molecules. This makes it an important concept in studies involving chemistry and environmental science.