Question

Calculate no of atoms in 42g of oxygen and molecules present in 126 g of CO2

Answer 1

First let us see what is the atomic mass of oxygen
which is 16
therefore 16 g of oxygen contains 1 mole of oxygen
42 g of oxygen will contain =42/16=2.625 moles

we know that one mole of any substance contains 6.022*10^23
therefore 2.625 moles of oxygen will contain =2.625*6.022*10^23=15.80775 atoms

the molecular mass of CO2 is 44
therefore 44 g of CO2 contains 1 mole
126g of CO2 will contain =126/44=2.8636

therefore 2.8636 moles of CO2 will contain = 2.8636*6.022*10^23=17.244 atoms

hope this helped u :-)