Question

The \(\mathrm{pH}\) of a solution is 6.7 . From this statement alone, can you conclude that the solution is acidic? If not, what additional information would you need? Can the \(\mathrm{pH}\) of a solution be zero or negative? If so, give examples to illustrate these values.

Short answer

Yes, the solution is acidic because it has a pH less than 7. Yes, a solution can have a pH of zero or even negative as in the case of highly concentrated strong acids like hydrochloric acid.

Step-by-step solution

Problem Analysis

To determine if a solution is acidic or basic, we analyze the pH value. Given the pH value of the solution is 6.7 and we know that a solution with pH less than 7 is acidic. Therefore we can say that this solution is acidic.

The pH spectrum

It's important to understand that pH scale ranges from 0 to 14. A pH of 7 is neutral. Values below 7 indicate an acidic solution and values above 7 indicate a basic, or alkaline, solution.

Negative and Zero pH

While it's not commonly found, theoretically, the pH of a solution can be zero or even negative. Such extreme acidity usually occurs in high concentrations of strong acids. An example is the hydrochloric acid (HCl), when concentrated it can have negative pH values.

Key concepts

Understanding Acidic Solutions

An acidic solution is characterized by having a pH value less than 7. When a solution has a pH of 6.7, as stated in the original exercise, it is classified as acidic. The pH scale operates as a measure of hydrogen ion concentration in a solution. In simpler terms, the lower the pH number, the higher the acidity. This is because a lower pH corresponds to a higher concentration of hydrogen ions (H⁺) in the solution.

Here are the key points to remember about acidic solutions:

• Solutions with pH less than 7 are considered acidic.
• The closer the pH value is to 0, the stronger the acid strength.
• Common examples include lemon juice, vinegar, and stomach acid.

Understanding the characteristics of an acidic solution helps in predicting its behavior in chemical reactions and its interactions with various materials.

Neutral pH Explained

A solution with a neutral pH has a pH of exactly 7. This is a balanced state and indicates that the concentrations of hydrogen ions (H⁺) and hydroxide ions (OH⁻) are equal. In pure water at room temperature, this balance is naturally achieved, giving it a neutral pH.

Here are some important aspects about neutral pH:

• Neutral pH is a central point on the pH scale, representing neither acidic nor basic conditions.
• Substances with neutral pH are often harmless and non-reactive, making them safe for most uses.
• Neutral solutions are essential in various chemical and biological processes, providing stable environments.

Understanding neutral pH is crucial for maintaining the balance in living organisms and creating safe artificial environments.

Exploring Negative pH

While the typical pH scale ranges from 0 to 14, a solution can theoretically have a pH below 0, known as a negative pH. This occurs in solutions with extremely high concentrations of hydrogen ions. Negative pH values are not commonly encountered in everyday life but are possible in concentrated strong acids.

To put this into perspective:

• Negative pH values indicate extreme acidity, more so than a pH of 0.
• Such cases usually involve industrial or laboratory-grade acids like concentrated hydrochloric acid (HCl).
• In practice, measuring negative pH requires specialized equipment due to the high acidity.

Understanding negative pH can be significant in fields dealing with extreme chemical reactions or industrial processes.