Do Inorganic Molecules Without Hydrogen Have pH Levels?

Introduction:

The pH of a substance is a measure of its acidity or basicity, which is typically defined by the concentration of hydrogen ions (H ) in an aqueous solution. However, it is often misconceived whether inorganic molecules without hydrogen, such as salts and other ionic compounds, can possess pH levels. This article delves into the nuances of this question and clarifies the conditions under which an aqueous solution containing such molecules can exhibit pH levels.

Understanding pH Levels

Before we dive into the question, it is essential to understand that the pH level is specifically a characteristic of aqueous solutions, not individual molecules. The pH is a logarithmic scale that measures the concentration of hydrogen ions (H or H3O in aqueous solutions). In pure water, at 25°C (298 K), the concentration of H ions is neutral, with a pH of 7. In acidic solutions, the concentration of H ions is greater than 10-7 moles per liter, resulting in a pH less than 7. In basic solutions, H ions are fewer, leading to a pH greater than 7.

Do Molecules Without Hydrogen Have pH Levels?

Wesley Whitfield’s response is more or less correct when stating that molecules do not have pH levels directly. Instead, it is the aqueous solutions of these molecules that have pH levels. This distinction is crucial for understanding the acid-base behavior in solutions.

Aqueous Solutions and pH:
Molecules such as salts and inorganic anions do not inherently possess pH levels because they are not free-floating in a pure medium. Instead, when dissolved in water, these substances can affect the pH of the resulting solution. For example, consider adding a strong acid like hydrochloric acid (HCl) or a strong base like sodium hydroxide (NaOH) to water.

Acids:
A strong acid like hydrochloric acid (HCl) will increase the concentration of H ions in the solution, leading to a pH less than 7. The equation for this process is:

HCl H2O → H3O Cl-

Conversely, a strong base like sodium hydroxide (NaOH) will increase the concentration of OH- ions, reducing the concentration of H ions, and thus, the pH will be greater than 7:

NaOH H2O → Na OH-

Special Cases: Anions and Cations

Anions Without Hydrogen:
Certain inorganic anions, such as phosphate (PO43-) from sodium phosphate (Na3PO4) or carbonate (CO32-) from sodium carbonate (Na2CO3), can affect the pH of a solution by interacting with water. For example, sodium acetate (-CH3CO2Na) can also contribute to a basic solution when dissolved in water:

-CH3CO2Na H2O → CH3COOH OH-

Cations and Their Effects:
While it is true that you cannot add aluminum ions (Al3 ) directly, adding salt like aluminum chloride (AlCl3) to water can result in a highly acidic solution. This is due to both the association of aluminum with water and the generation of HCl from the dissociation of AlCl3:

AlCl3 H2O → Al(OH)3 HCl

The acidity here is due to the HCl produced, as well as the association of water with Al3 .

Conclusion

In conclusion, while individual inorganic molecules without hydrogen, such as salts and anions, do not have pH levels directly, their dissolution in water can indeed change the pH of the resulting solution. The core concept is that pH is a measure of the concentration of H ions in an aqueous solution and is influenced by the components added to it. Whether a solution becomes acidic, basic, or remains neutral depends on the balance of H and OH- ions in the solution.

Key Takeaways: - pH is a measure specific to aqueous solutions, not individual molecules. - The dissolution of inorganic compounds in water can alter the pH of the solution. - Strong acids and bases directly affect pH by increasing or decreasing the concentration of H ions.