Natural abundance of heavy water in water is `1: 6000`. How many heavy water molecules are present in one drop of water ? (one mL water is 20 drops)

Explanation

one mL water = one gram (`because` d = 1 g per mL)
weight of one drop of water `=(1)/(20)g`
weight of `D_(2)O` in one drop of water `= (1)/(20xx6000)`
Number of moles of `D_(2)O=("weight")/("GMW")=(1)/(20xx6000xx20)`
  Number of moles of `D_(2)O`  molecules = Number of molecules `xxN_(A)`
`=(6.022xx10^(23))/(20xx6000xx20)=2.51xx10^(17)`
Number of heavy water molecules is `2.51xx10^(17)`