Density of water at room temperature is 1 g/ml. How many molecules are there in a drop of water, if its volume is 0.05 ml?

Options

A. (a)`1.67xx10^(21)`
B. (b)`16.7xx10^(21)`
C. (c )`6.023xx10^(23)`
D. (d)`1.67xx10^(23)`

Answer

a

Explanation

Density of water at room temperature `=1 g//"mol"`
`:. 1 ml` contain `1/18` moles of `H_(2)O`
`0.05 ml` will contain `0.05xx1/18` moles
`:. 1 "mole"=6.022xx10^(23)` moles
Total number of molecules in a drop of water
`=6.023xx10^(23)xx0.05xx1/18=1.67xx10^(21)`