Why does a neutral solution have a pH of 7.0?

검증된 단계별 안내

Understand the concept of pH: pH is a measure of the hydrogen ion concentration ([H⁺]) in a solution. It is calculated using the formula:

pH = - \log_{10} ([H⁺])

Recognize the definition of a neutral solution: A neutral solution is one where the concentrations of hydrogen ions ([H⁺]) and hydroxide ions ([OH⁻]) are equal. This occurs in pure water at 25°C.

Recall the ion-product constant for water (Kw): At 25°C, water undergoes self-ionization, producing equal amounts of H⁺ and OH⁻ ions. The ion-product constant is given by:

K_{w} = [H⁺] \times [OH⁻] = 1.0 \times 10^{- 14}

Determine the [H⁺] in a neutral solution: Since [H⁺] = [OH⁻] in a neutral solution, we can solve for [H⁺] by taking the square root of Kw:

[H⁺] = \sqrt{1.0 \times 10^{- 14}}

Calculate the pH of a neutral solution: Substitute the value of [H⁺] into the pH formula. For a neutral solution at 25°C, this results in a pH of 7.0, which is the midpoint of the pH scale (ranging from 0 to 14).

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

도움이 되었나요?

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, indicating that the concentration of hydrogen ions (H+) is equal to that of hydroxide ions (OH-). Values below 7 represent acidic solutions, while values above 7 indicate basic solutions.

Water Ionization

Water (H2O) can dissociate into hydrogen ions (H+) and hydroxide ions (OH-) in a process called ionization. In pure water at 25°C, this dissociation occurs to a very small extent, resulting in equal concentrations of H+ and OH-, which is approximately 1 x 10^-7 moles per liter, leading to a neutral pH of 7.

Equilibrium in Pure Water

In a neutral solution, the equilibrium between H+ and OH- ions is maintained, meaning that any addition of acids or bases will disrupt this balance. At a pH of 7, the concentrations of H+ and OH- are equal, demonstrating that pure water is neither acidic nor basic, thus maintaining its neutral status.