Question

calculate the no. of water molecular in a drop 0.0018 ml at room temp (density of h₂0 =1gm/m

Answer 1

• 0.0018ml=0.0018g

Molar mass of H_20

$\\ \sf\longmapsto 2(1u)+16u$

$\\ \sf\longmapsto 16u+2u$

$\\ \sf\longmapsto 18g/mol$

Now

$\boxed{\sf No\;of\:moles=\dfrac{Given\:Mass}{Molar\:Mass}}$

$\\ \sf\longmapsto No\:of\;moles=\dfrac{0.0018}{18}=0.0001mol$

Now

$\boxed{\sf No\;of\;molecules=No\:of\;moles\times Avagadro\:No}$

$\\ \sf\longmapsto 0.0001\times 6.023\times 10^{23}$

$\\ \sf\longmapsto 0.0000166\times 10^{23}$

$\\ \sf\longmapsto 1.6\times 10^{18}molecules$