(a)What do the following observations stand for?
(i)2O (ii)`3O_(2)`
(b)Which amongst the following has more number of atoms and how much?
(i)11.5g of sodium (ii)15.0g of calcium

Explanation

Gram atomic mass of sodium (Na)=23g
23g of sodium have atoms=`N_(A)`
11.5g of sodium have atoms `=0.5xxN_(A)=0.5xx6.022xx10^(23)`
`=3.011xx10^(23)`
Gram atomic mass of calcium (Ca)=40g
40g of Calcium have atoms =`N_(A)`
15g of calcium have atoms `=(15)/(40)xxN_(A)=0.375xx6.022xx10^(23)`
`=2.258xx10^(23)`
11.5g of sodium has more atoms=`(3.011-2.258)xx10^(23)`
`=7.53xx10^(22)"atoms:`