N2O4 on decomposition gives its monomer NO2 and they are found to be in equilibrium at 300 K. if the VD of such a mixture is 41.4 the calculate % composition by (1) Moles of NO2 and N2O4 (2) By mass O2

Answer Key: (1) 20% and 80% (2) 11.1%

A compound of nitrogen and oxygen was found to contain 7: 16 by mass N and O respectively. Calculate molecular formula if vapour density is 46.

 Answer Key: ( N2O4)

A mixture of blue and green balls contains 25% by number blue balls. Mass of each blue balls is 40 gm and mass of each green balls is 20 gm calculate (1) Average mass of ball (2) % by mass

Answer Key: (1) 25 gm (2) 40 %

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%