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Sodium Hydroxide (NaOH)

• Sodium hydroxide (NaOH) -
  
  
  • Is usually dispensed as semi spherical pellets.
    
    
  • Is a caustic substance and skin contact should be avoided.
    
    
  • Is hydroscopic (ie will absorb water from the air when exposed).
    
    This means that an accurate, dry weight is difficult to determine
    
    
  • NaOH (sodium hydroxide), when exposed to the air, will react with the carbon dioxide in air, to form sodium carbonate (see equation).
    
    This means that sodium hydroxide as a solid or in solution will loose its strength with time and degree of exposure and solutions of NaOH will need to be standardised.
    
    
    
• Sodium hydroxide (NaOH) ionises in water as shown by the following equation -
  
  

  NaOH

  +

  H2O

  <=>

  Na+

  +

  OH-

  +

  H2O

  
  
  This equation shows that in solution NaOH will release hydroxide ions (OH^-).
  
  The excess of OH^- ions in solution causes that solution to be basic or alkaline and caustic.
  
  
  
• Sodium hydroxide (NaOH) solution and Titration-
  
  
  0.1 M NaOH is used as the titrant in the determination of titratable acidity and volatile acidity.
  
  0.01 M NaOH is used as the titrant in the determination of SO₂ (sulphur dioxide).
  
  
  
• Sodium hydroxide's (NaOH) Molecular Weight -
  
  
  The molecular weight of NaOH is 40
  
  ie AW of Na = 23, O = 16 and H = 1
  
  therefore 23 + 16 +1 = 40