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
#Avogadro's number of oxygen atoms# has a special property: #N_A# #oxygen atoms#, #6.022xx10^23# individual oxygen atoms have a mass of #15.999*g# precisely. This is why educators go to such lengths to teach the mole. It is the link between the micro world of atoms and molecules, to the macro world of grams, and kilograms, and litres.