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
Since there are 2 hydrogens in the molecule, the total weight of hydrogen in water is 2 times 1.00794, or 2.01588. There is only 1 oxygen, so the total weight of oxygen is 15.9994. Finally, we add up the weights of all the atoms to get the total molecular weight of water, 18.0153 grams per mole.