Kw

• Kw = [H+] [OH-]
• Increasing temperature, increases Kw because equilibrium shifts to the right hand side (endothermic reaction ) so more products are produced
• Using Kw to calculate the pH of strong bases e.g,

  Strong bases fully dissociates to form OH- ions so if [NaOH] = 0.195 moldm^-3 then [OH-] = 0.195

  At 298k, Kw = 1*10-14 mol2dm-6

  • Kw = [H+] [OH-]
  • Rearrange equation to find [H+]
  • Then find pH using -log[H+]
• Why is [H2O] not shown in the Kw expression?

  • Water is almost constant
  • It's concentration is very large compared to [H+] and [OH-]