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Molecular weight (MW)

• Molecular weight (MW) is similar to atomic weight but applies to one complete molecule .
  
  
  • Example (1): Water (H₂O) is made up of -
    
    
    1 atom of hydrogen (H - atomic weight (AW) = 1) and
    
    two atom of oxygen (O- AW (atomic weight) = 16)
    
    and therefore H₂O (water) has a molecular weight (MW) of 33
    
    ie MW of H₂O = 33
    
    ie (1 + (2 x 16) = 33)
    
    
  • Example 2: MW of NaOH = (Na)23 + (O)16 + (H)1 = 40
    
    
• A substance's molecular weight in grams is one mole of that substance.
  
  
  • Example (1): 40 grams of NaOH = 1 mole of NaOH
    
    
• AWs of elements can be found in the following table