The number of water molecules present in a drop of water (volume 0.0018 ml) density = 1 `gmL^-1` at room temperature is

Options

A. `6.023 xx 10^(19)`
B. `1.084 xx 10^(18)`
C. `4.84 xx 10^(17)`
D. `6.023 xx 10^(23)`

Answer

A

Explanation

Density `= ("Mass")/("Volume") ,1 = (g)/(mL) ` or g = mL
`0.0018 mL = 0.0018 g`
No.of moles ` = ("weight")/("Molecular weight") = (0.0018)/(18) = 1 xx 10^(-4)`
`therefore` No. of water molecules `=6.023 xx 10^(23) xx 1 xx 10^(-4) = 6.023 xx 10^(19)`