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pH and pOH Equations:
At 25°C: pK_w = 14
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pH and pOH are logarithmic measures of the acidity and basicity of aqueous solutions. pH measures hydrogen ion concentration while pOH measures hydroxide ion concentration. They are inversely related through the water dissociation constant.
The calculator uses the following equations:
At 25°C: pK_w = 14
Where:
Explanation: The equations convert concentration values to a logarithmic scale that is more convenient for working with the wide range of concentrations found in aqueous solutions.
Details: Accurate pH and pOH calculations are essential for chemical analysis, water treatment, biological systems, industrial processes, and environmental monitoring. They help determine the acidity or basicity of solutions.
Tips: Enter hydrogen ion concentration and hydroxide ion concentration in mol/L. Both values must be positive numbers. The calculator will compute the corresponding pH and pOH values.
Q1: What is the relationship between pH and pOH?
A: pH + pOH = 14 at 25°C. This relationship comes from the water dissociation constant K_w = [H⁺][OH⁻] = 10⁻¹⁴.
Q2: What are typical pH values for common substances?
A: Pure water has pH 7, lemon juice around 2, baking soda solution around 8.5, and bleach around 12-13.
Q3: Why use logarithmic scales for pH and pOH?
A: Logarithmic scales compress the wide range of hydrogen ion concentrations (from 1 to 10⁻¹⁴ mol/L) into a more manageable scale from 0 to 14.
Q4: Does temperature affect pH calculations?
A: Yes, the water dissociation constant K_w changes with temperature, which affects the pH + pOH relationship. At different temperatures, pK_w may not equal 14.
Q5: Can I calculate one value if I know the other?
A: Yes, if you know pH, you can calculate pOH = 14 - pH (at 25°C), and vice versa. You can also calculate concentrations from pH or pOH values.