A sample of ethane `( C_(2) H_(6))` gas has the same mass as `1.5 xx 10^(20)` molecules of methane `( CH_(4))` . How many `C_(2) H_(6)` molecules does the sample of gas contain?

Explanation

16g of methane contains `6.022 xx 10^(23)` molecules
Mass of `1.5 xx 10^(20)` molecules of methane `= ( 16 xx 1.5 xx 10^(20))/( 6.022 xx 10^(23) ) g `
30g of ethane contains `6.022 xx 10^(23)` molecules.
`( 16 xx 1.5 xx 10^(20))/( 6.022 xx 10^(23)) g ` of ethane contains
`= ( 6. 0 22 xx 10^(23))/( 30) xx ( 16 xx 1.5 xx 10^(20))/(6.022 xx 10^(23)) = 8 xx 10^(19)` molecules.