ChemicalData of O returns the values of water...
In[16]:= ChemicalData["O", "MolarMass"]
Out[16]= Quantity[18.0153, ("Grams")/("Moles")]
Calculation of MolarMass of Silver bromate (AgBrO3) is also inconsistent:
In[17]:= ChemicalData["AgBrO3", "MolarMass"]
Out[17]= Quantity[236.778, ("Grams")/("Moles")]
Instead of the actual valur of: 235.771
