Acidity and Alkalinity

• Acidity


  • depends on the concentration of hydrogen ions relative to that of hydroxide ions in a solution
  • if concentration of hydrogen ions is higher than that of hydroxide ions, the solution is acidic
• Alkalinity


  • Alkalinity depends on the concentration of hydroxide ions relative to that of hydrogen ions in a solution
  • if concentration of hydroxide ions is higher than that of hydrogen ions, the solution is alkaline
• Neutral solution


  • concentrations of hydrogen ions and hydroxide ions are the same
• pH scale


  • the lower the pH value, the higher the concentration of hydrogen ions compared to hydroxide ions, higher acidity
  • the higher the pH value, the higher the concentration of hydroxide ions compared to hydrogen ions, higher alkalinity
• Universal Indicator


  • pH level 1 : red
  • pH level 3 : orange
  • pH level 5 : yellow
  • pH level 7 : green
  • pH level 9 : turquoise
  • pH level 11 : blue
  • pH level 13 : violet
• Indicators

  • methyl orange : red to yellow (3 to 5)
  • screened methyl orange : violet to green (3 to 5)
  • bromothymol blue : yellow to blue (6 to 8)