Total particles in 1 mole of oxygen = 6.023 moles.'
Nuclear number of oxygen is 8 , atomic weight is 16 .
Test 1 has oxygen as 18/16 = 9/8 proportion .
In this manner normal mass of both the proportion is = 9/8 x 16 = 18
In this manner test 1 has 2 more oxygen iotas than the main specimen.