Question

Of the following conditions, which indicate a basic solution? a. \(\mathrm{pOH}=12.53\) b. \(\mathrm{pH}=3.64\) c. \(\mathrm{pOH}<\left[\mathrm{H}^{+}\right]\) d. \(\left[\mathrm{OH}^{-}\right]>1.0 \times 10^{-7} M\)

Short answer

Option (d), [\(\mathrm{OH}^{-}\)] > 1.0 × 10⁻⁷ M, indicates a basic solution.

Step-by-step solution

Check if the pOH value indicates a basic solution

For option (a), we are given a pOH value of 12.53. To check if this indicates a basic solution, we will first find the corresponding pH value by using the formula pH + pOH = 14. So, the pH value will be 14 - 12.53, which is equal to 1.47. Since the pH value is less than 7, this indicates an acidic solution, not a basic one. So, option (a) is incorrect.

Check if the pH value indicates a basic solution

For option (b), we are given a pH value of 3.64. Since the pH value is less than 7, this indicates an acidic solution, not a basic one. So, option (b) is incorrect.

Check if the condition between pOH and [\(\mathrm{H}^{+}\)] indicates a basic solution

For option (c), we are given the condition that pOH < [\(\mathrm{H}^{+}\)]. This condition does not indicate the pH value or the acidity/basicity of the solution, and thus we cannot make a conclusion based on this condition. So, option (c) is incorrect.

Check if the condition [\(\mathrm{OH}^{-}\)] > 1.0 × 10⁻⁷ M indicates a basic solution

For option (d), we are given the condition that [\(\mathrm{OH}^{-}\)] > 1.0 × 10⁻⁷ M. In a neutral solution, the concentration of the hydroxide ion is equal to 1.0 × 10⁻⁷ M. If the hydroxide ion concentration is higher than 1.0 × 10⁻⁷ M, it means that the solution has more hydroxide ions than a neutral solution, and thus is a basic solution. So, option (d) is the correct answer.

Key concepts

pH and pOH

In the world of acid-base chemistry, understanding pH and pOH is crucial. These are scales used to measure the acidity and basicity of a solution. The pH scale measures how acidic or basic a solution is. Meanwhile, pOH helps us understand the concentration of hydroxide ions in a solution. These scales are intimately connected by the equation \( \text{pH} + \text{pOH} = 14 \).

This equation shows that when you know the pH of a solution, you can easily find its pOH, and vice versa. A solution with a pH less than 7 is acidic, whereas a solution with a pH greater than 7 is basic. For example, if a solution has a pOH of 12.53, the pH would be \( 14 - 12.53 = 1.47 \), indicating an acidic solution. On the other hand, if the pH is low, say 3.64, it also indicates acidity.

It's essential to be fluent with these conversions, as they allow us to toggle between the degrees of acidity and basicity with ease.

• pH measures hydrogen ion concentration \([\text{H}^+]\)
• pOH measures hydroxide ion concentration \([\text{OH}^-]\)
• Remember: \( \text{pH} + \text{pOH} = 14 \)

hydroxide ion concentration

The concentration of hydroxide ions, \([\text{OH}^-]\), plays a key role in determining the nature of a solution. In a neutral solution at 25°C, both hydrogen \([\text{H}^+]\) and hydroxide ions \([\text{OH}^-]\) have concentrations of \(1.0 \times 10^{-7} \text{ M}\). When the hydroxide ion concentration is greater than this value, the solution becomes basic.

For example, if we find that \([\text{OH}^-]\) is greater than \(1.0 \times 10^{-7} \text{ M}\), it indicates a basic solution. This is because an increased concentration of hydroxide ions shifts the balance away from neutrality. Conversely, if the concentration is less, it suggests an acidic solution.

Moreover, knowing \([\text{OH}^-]\) can help derive the pOH, which further helps describe the solution's basicity. Understanding how these ion concentrations interact gives power to predict and control the reaction environment.

• \([\text{OH}^-]\) higher than \(1.0 \times 10^{-7} \text{ M}\) means basic
• Used to derive pOH
• Key determinant in assessing solution's nature

acidic and basic solutions

Acidic and basic solutions are fundamental concepts in chemistry distinguished by their pH levels. An acidic solution has a pH below 7, indicating a higher concentration of hydrogen ions. Basic solutions, on the other hand, have a pH greater than 7, meaning a higher concentration of hydroxide ions.

Understanding these properties helps one ascertain the characteristics of the solution. For instance, if \([\text{OH}^-]\) exceeds \(1.0 \times 10^{-7} \text{ M}\) in a solution, it suggests basicity due to the increased presence of hydroxide ions. Conversely, the more hydrogen ions present, the more acidic the solution becomes.

This classification helps predict how a solution will behave in chemical reactions, such as whether it will accept or donate protons. Recognizing whether a solution is acidic or basic is crucial in fields ranging from organic chemistry to environmental science.

• Acidic: pH < 7, high \([\text{H}^+]\)
• Basic: pH > 7, high \([\text{OH}^-]\)
• Influence on chemical reactivity and interaction