Question

The \(\mathrm{pH}\) of solutions \(\mathrm{A}, \mathrm{B}, \mathrm{C}\) and \(\mathrm{D}\) are \(9.5,2.5,3.5\) and \(5.5\), respectively. The most acidic solution is (1) \(\mathrm{A}\) (2) \(\mathrm{B}\) (3) \(\mathrm{C}\) (4) D

Short answer

Solution \(\text{B}\) with a \(\mathrm{pH}\) of \(2.5\) is the most acidic.

Step-by-step solution

Understand \(\mathrm{pH}\)

To determine the acidity of a solution, use the \(\mathrm{pH}\) scale. The \(\mathrm{pH}\) scale ranges from 0 to 14. A \(\mathrm{pH}\) less than 7 is acidic, a \(\mathrm{pH}\) of 7 is neutral, and a \(\mathrm{pH}\) greater than 7 is basic.

Compare \(\mathrm{pH}\) values

Identify which of the given \(\mathrm{pH}\) values is the lowest. The given \(\mathrm{pH}\) values are: \(9.5\) for solution \(\text{A}\), \(2.5\) for solution \(\text{B}\), \(3.5\) for solution \(\text{C}\) and \(5.5\) for solution \(\text{D}\).

Determine the most acidic solution

The solution with the lowest \(\mathrm{pH}\) value is the most acidic. Among the given \(\mathrm{pH}\) values, \(\text{B}\) with a \(\mathrm{pH}\) of \(2.5\) is the lowest.

Key concepts

Acidity Determination

Acidity in chemistry is all about the concentration of hydrogen ions \(\text{H}^+\) in a solution. The more hydrogen ions a solution has, the more acidic it is. We measure this acidity using the \(\text{pH}\) scale. The \(\text{pH}\) scale ranges from 0 to 14. Here's a critical aspect to remember:

• A \(\text{pH}\) value less than 7 indicates an acidic solution.
• A \(\text{pH}\) value of exactly 7 is considered neutral, like pure water.
• If the \(\text{pH}\) value is more than 7, the solution is basic (or alkaline).

So, for our given solutions, we can determine their acidity by checking where they fall on the \(\text{pH}\) scale. Solution B has a \(\text{pH}\) of 2.5, solution C has a \(\text{pH}\) of 3.5, and solution D has a \(\text{pH}\) of 5.5. Therefore, solution B is the most acidic since it has the lowest \(\text{pH}\).

Solution Comparison

When we compare the acidity of different solutions, we primarily look at their \(\text{pH}\) values. The \(\text{pH}\) value tells us how acidic or basic a solution is. Here's a simple way to compare:

• The lower the \(\text{pH}\) value, the more acidic the solution is.
• Conversely, the higher the \(\text{pH}\), the more basic the solution is.
• Notice that the difference in \(\text{pH}\) values is logarithmic. This means a small change in \(\text{pH}\) indicates a significant change in \(\text{H}^+\) concentration.

For instance, moving from a \(\text{pH}\) of 3 to 2 doesn't just double the acidity; it makes it 10 times more acidic! This is because the \(\text{pH}\) scale is logarithmic (base 10). Comparing solutions A (9.5), B (2.5), C (3.5), and D (5.5), we see Solution B is the most acidic, followed by C, D, and then A.

Chemistry Fundamentals

At the heart of understanding acidity is the basic chemistry concept of ions and molecules in a solution. Here are a few fundamentals:

• Acids release hydrogen ions (\(\text{H}^+\)) when dissolved in water.
• Bases release hydroxide ions (\(\text{OH}^-\)) when dissolved in water.
• The \(\text{pH}\) scale measures the concentration of hydrogen ions in a solution. The formula is \(\text{pH} = -\text{log}[\text{H}^+]\).

Remember, a strong acid fully dissociates in water, releasing more \(\text{H}^+\) ions. This results in a lower \(\text{pH}\) and higher acidity. Understanding these concepts can help you interpret the behavior of various solutions. For example, picking the most acidic solution is straightforward when you understand the \(\text{pH}\) scale and its logarithmic nature.