It could not hold good for elements heaver than calcium.
        
             
        
        
        
Answer:
6.21 moles O
Explanation:
To find the moles of oxygen, you need to (1) convert grams Mn(ClO₄)₄ to moles Mn(ClO₄)₄ (via molar mass) and then (2) convert moles Mn(ClO₄)₄ to moles O (via mole-to-mole ratio from formula subscripts). It is important to arrange the conversions/ratios in a way that allows for the cancellation of units.
Molar Mass (Mn(ClO₄)₄): 452.74 g/mol
1 Mn(ClO₄)₄ = 1 Mn and 4 Cl and 16 O
 175.7 g Mn(ClO₄)₄           1 mole                   16 moles O
---------------------------  x  -------------------  x  ---------------------------  =  6.21 moles O
                                        452.74 g            1 mole Mn(ClO₄)₄
 
        
             
        
        
        
Answer:
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus and minus signs.
Explanation:
 
        
             
        
        
        
check out this website 
https://www.convertunits.com/
0.11746 dag for 13 a
9.930139 dag for 19a