Question

At \(25^{\circ} \mathrm{C}\) the \(\mathrm{pH}\) value of a solution is 6 , the solution is: (a) Neutral (b) Acidic (c) Alkaline (d) Basic

Short answer

The solution is acidic (b).

Step-by-step solution

Understand pH Scale

The pH scale measures how acidic or basic a solution is, ranging from 0 to 14. A pH of 7 is neutral, a pH less than 7 indicates an acidic solution, and a pH greater than 7 signifies a basic (or alkaline) solution.

Determine pH Category

Given that the pH is 6, compare this value to the neutral pH value of 7. Since 6 is less than 7, the solution is classified as acidic.

Answer the Question

Based on the information about the pH scale and the given pH value of 6, the solution must be acidic.

Key concepts

Acidic Solution

In order to understand what an acidic solution is, we first need to grasp the pH scale. The pH scale ranges from 0 to 14 and helps determine the acidity or basicity of a substance. An acidic solution has a pH value less than 7. This implies a higher concentration of hydrogen ions.
When you have a solution with a pH value of 6 at 25°C, it is classified as an acidic solution because its pH is lower than the neutral point of 7.
Common everyday examples of acidic solutions include:

• Lemon juice (pH around 2)
• Vinegar (pH around 3)
• Stomach acid (pH around 1.5 to 3.5)

These substances feature high concentrations of hydrogen ions, making them tangy or sour to taste. A good trick is to remember that the lower the pH, the more acidic the solution.

pH Value Interpretation

Interpreting a pH value involves understanding where a particular value sits on the pH scale. Each number on the scale indicates a tenfold difference in ion concentration.
Therefore, even a small shift in pH represents a significant change in acidity or basicity.
A pH of 7 is neutral, meaning the concentration of hydrogen ions equals that of hydroxide ions.
When a pH value is below 7, like 6 from our exercise, it means there's a higher concentration of hydrogen ions relative to hydroxide ions, hence the acidic nature.
To interpret pH effectively:

• Values less than 7 = Acidic
• Values equal to 7 = Neutral
• Values greater than 7 = Basic

Interpreting pH this way aids in understanding the chemical nature of solutions and how they might react with other substances.

Basic (Alkaline) Solution

A basic or alkaline solution stands in contrast to an acidic solution. It has a pH value greater than 7. This indicates a lower concentration of hydrogen ions and a higher concentration of hydroxide ions.
Such solutions are typically slippery and bitter in taste.
Household and industrial examples of basic solutions might include:

• Ammonia (pH around 11)
• Baking soda (pH around 9)
• Soap solutions (pH around 10)

Alkaline solutions tend to neutralize acids in reactions, which is why they are often used in cleaning supplies.
When you understand that a pH above 7 shows decreasing acidity and increasing basicity, it becomes easier to identify substances as more basic or alkaline.