---

INPUT   DATA

♥ EXAMPLE Of Input/Output

How To Use:  Type a number in the box you know, and press the Calculate button. Computed values for the remaining boxes are shown under "Output variables" below.

Hydrogen ions concentration, [H+]		M
Hydroxyl ions concentration, [OH-]		M
pH
pOH

---

---

OUTPUT   VARIABLES   &   GRAPHS

Variables	Values	Units
♦  Hydrogen ions concentration, [H+]		M
♦  Hydroxyl ions concentration, [OH-]		M
♦  pH
♦  pOH
♦  Acidity/Basicity of solution

Ionization Of Water

Water is amphiprotic, i.e. can act both as an acid and as a base. At any particular moment, a certain amount of water molecules H2O will disassociate into hydrogen (H+) and hydroxyl (OH-) ions, and within a very short time will re-assocaite again to form water. The water auto-ionization equilibrium must always be satisfied:

     K_w = [H⁺][OH^-] = [10^-14]

By definition, the acidity or alkalinity of a solution is often expressed by its pH or pOH which are expressed as follows:

     pH = -log₁₀[H⁺]
     pOH = -log₁₀[OH^-]
     pH + pOH = -log₁₀K_w = 14

where
     [H⁺] = molar concetration of hydrogen ions in the solution
     [OH⁺] = molar concetration of hydroxyl ions in the solution
     K_w= equilibrium constant of water

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY

• Posenberg JL & Epstein LM; College Chemistry, Schaum's Outlines Series; McGraw Hill, New York, 1997.
• Stephenson FH; Calculations For Molecular Biology And Biotechnology: A guide to mathematics in the laboratory; Academic Press, An Imprint of Elsevier, Amsterdam, 2003