Calculate The Ph of 0.075m Koh at The Following Temperatures

Introduction

Potassium hydroxide (KOH) is a strong base that completely dissociates in water to form K⁺ and OH⁻ ions. The pH of a KOH solution can be calculated using the concentration of hydroxide ions, which is affected by temperature.

The pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration:

For a strong base like KOH, the concentration of hydroxide ions ([OH⁻]) is equal to the concentration of the base (0.075 M in this case). The concentration of hydrogen ions ([H⁺]) can be calculated using the ion product of water (Kw), which is temperature-dependent.

How to Use This Calculator

1. Enter the temperature in degrees Celsius in the calculator.
2. Click the "Calculate" button to compute the pH.
3. View the result and interpretation.
4. Use the chart to visualize pH changes at different temperatures.

Formula Used

The pH of a KOH solution is calculated using the following steps:

1. Calculate the ion product of water (Kw) at the given temperature using the equation:

   Kw = 10^(-14.47 + 3299.2/T + 21.14*log10(T/298.15) - 3.24*10⁻³*T + 7.92*10⁻⁶*T²)

   where T is the temperature in Kelvin.
2. Calculate the concentration of hydrogen ions ([H⁺]) using the Kw and the concentration of hydroxide ions ([OH⁻]):

   [H⁺] = Kw / [OH⁻]

3. Calculate the pH using the hydrogen ion concentration:

   pH = -log[H⁺]

Worked Example

Let's calculate the pH of 0.075 M KOH at 25°C (298.15 K):

1. Calculate Kw at 25°C:

   Kw = 10^(-14.47 + 3299.2/298.15 + 21.14*log10(298.15/298.15) - 3.24*10⁻³*298.15 + 7.92*10⁻⁶*298.15²)

   Kw ≈ 1.0 × 10⁻¹⁴ M²

2. Calculate [H⁺]:

   [H⁺] = Kw / [OH⁻] = 1.0 × 10⁻¹⁴ / 0.075 ≈ 1.33 × 10⁻¹³ M

3. Calculate pH:

   pH = -log(1.33 × 10⁻¹³) ≈ 12.87

The pH of 0.075 M KOH at 25°C is approximately 12.87.

Effects of Temperature on pH

The pH of a KOH solution changes with temperature because the ion product of water (Kw) is temperature-dependent. As temperature increases, Kw increases, which means [H⁺] decreases and pH increases.

The table shows that the pH of 0.075 M KOH increases slightly with temperature, as expected for a strong base.