A 1 L flask cantaing vapours of methyl alcohol (molar mass 32) at a pressure was `10^(-3)` mm. How many molecules of mehtyl alcohol are left in the flask ?

Answer

A, B, C, D

Explanation

`P_(1)=10^(-3)mm, V_(1)=1000 cm^(3), T_(1)=298 K`
For converting this volume to volume at S.T.P. , apply
`(P_(1)V_(1))/(T_(1))=(P_(2)V_(2))/(T_(2)), i.e., (10^(-3)xx1000)/(298)=(760xxV_(2))/(273)" or " V_(2)=1.205xx10^(-3)cm^(3)`
`22400 cm^(3)` at S.T.P.`-=6.02xx10^(23)` molecules
`:. 1.205xx10^(-3)cm^(3)` at S.T.P. `-=(6.02xx10^(23))/(22400)xx1.025xx10^(-3)` molecules `=3.24xx10^(16)` molecules