Air contains 20% of O2 and 80 % N2 by moles find the average molecular mass weight and % by mass of oxygen and nitrogen.

Answer Key:  Mav = 23.8 amu ,  %  by mass of Oxygen =  22.3 %  and % by mass of Nitrogen is 77.7 % 

An element X have three isotopes X ^20 ,X ^21 and X ^22 . The percentage abundance of X^20 is 90% and the average atomic mass of element is 20.18. The percentage abundance of X ^21 should be

 Answer Key: 2%

Calculate Average atomic mass of Argon the natural abundance % of isotopes of Argon is given as:

Answer Key: 39.94 amu

Calculate the average atomic mass of silicon if relative abundance is 92.23 ,isotope Si^28, 4.77 % isotope = Si^29 and 3% isotope = Si^39 .

Answer Key: The average atomic mass of silicon is 28.1 amu

Silver contains two isotopes Ag 107 and Ag109 and average atomic weight of silver is 108.5 find percentage abundant of isotopes of silver.

 Answer Key: Ag (107) 25% and Ag (109) 75%