Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. They are used as anticoagulant medications in the prevention of thrombosis, and in pest control, as rodenticides. 1  1 Mechanism of action.  2 Coumarins (4-hydroxycoumarins)
Calculate the average atomic mass of oxygen. Solution: ((15.994915*99.757) + (16.999132*0.038) + (17.999160*0.205))/100 = 15.999405 . Using our equation for determining average atomic mass, we see that the average atomic mass for oxygen is 15.999405 amu. If we check the periodic table, we will see that our average atomic mass is the same as the atomic mass indicated on the element oxygen. Ã
Mass of phosphorus = 31.0 g/mol x 1 mol = 31.0 g of phosphorus. Step 5: Divide the mass of phosphorus by the molar mass of Na3PO4 and multiply by 100%. to get percent mass. Percent mass of phosphorus = 31.0g x 100% = 18.9 % P. 164 g. Step 6: Find the total mass of all the oxygen atoms in one mole of the compound.