Question

What will be the number of molecules in  10 mL water vapour at S.T.P. ?

Answer 1

At S.T.P., volume of 6.022 × 10²³ molecules = 22.4 L 

At S.T.P., 22400 mL water vapour contains  = 6.022 × 10²³ molecules .

So, at S.T.P., 10 mL of water vapour will contain 

\( = \frac{6.022\times 10^{23}\times 10}{22400}\)

= 2.69 × 10²⁰ molecules