Calculate the number of water molecules present in one drop of water which weights 0.18 g.

Explanation

Mass of water = 0.18 g
No of mol es`=(Mass)/("Molecular Mass")`
`=(0.18)/(18)=(0.01)mol e`
Number of molecules = Number of moles `xx` Avogadro number
`= 0.01 xx 6.023 xx 10^(23)`
`= 0.06023 xx 10^(23)`
` = 6.023xx 10^(21) `molecules
(ii) Calculate the number of moles in `1.51 xx 10^(23)` molecules of `NH_(4)CI`
`No of mol es = ("Number of molecules")/("Avogadro number")`
`= (1.51xx10^(23))/(6.023 xx 10^(23))`(iii) Calculate the gram of 5 moles of sulphur molecule, `S_(8)`
5 moles of sulphur molecule `S_(8)`
Molecular mass of sulphur molecule `= 32 xx 8 = 256` Mass = No of moles `xx` molecular mass
`= 5 xx 256`
`= 1280 g`