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pH Formula:
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pH is a measure of the acidity or basicity of an aqueous solution. It is defined as the negative logarithm (base 10) of the hydrogen ion concentration [H+]. The pH scale ranges from 0 to 14, with 7 being neutral, values below 7 acidic, and values above 7 basic.
The calculator uses the pH formula:
Where:
Explanation: The logarithmic nature of the pH scale means each whole pH value below 7 is ten times more acidic than the next higher value, and each whole pH value above 7 is ten times more basic than the next lower value.
Details: pH is critical in many chemical and biological processes. It affects enzyme activity, chemical solubility, and biological functions. Maintaining proper pH is essential in medicine, agriculture, water treatment, and many industrial processes.
Tips: Enter the hydrogen ion concentration in molarity (M, mol/L). The value must be greater than 0. For very small concentrations, scientific notation may be helpful (e.g., 1.0E-7 for neutral water).
Q1: What is the pH of pure water?
A: At 25°C, pure water has a pH of 7 (neutral) with [H+] = 1.0 × 10⁻⁷ M.
Q2: What's the relationship between pH and pOH?
A: pH + pOH = 14 at 25°C. pOH is calculated similarly using hydroxide ion concentration [OH-].
Q3: Can pH be negative or greater than 14?
A: Yes, for very concentrated strong acids (pH < 0) or strong bases (pH > 14), though these are rarely encountered outside specialized laboratory conditions.
Q4: How does temperature affect pH?
A: The pH of neutral water changes with temperature (e.g., pH 7.47 at 0°C, 6.14 at 100°C) due to changes in water's autoionization constant.
Q5: What's the difference between pH and acidity?
A: pH measures hydrogen ion concentration, while acidity refers to a solution's ability to donate protons. A solution can have low pH (high [H+]) but weak acidity if it doesn't readily donate protons.