Question

A solution of palmitic acid (Molar mass $=256gm$ ) in benzene contains $5.12gm$ of acid per litre. When this solution is dropped on a surface, benzene evaporates and palmitic acid forms a monolayer. If we wish to cover an area of $480c{m}^2$ with a monolayer of volume $X\times 10^{-2}mL$ of solution should be used. Area occupied by one palmitic molecules $=0.2n{m}^2\}\left\{N_A=6\times 10^{23}\right\}$, Calculate value of $X?$ ?

Answer 1

Answer: 2

No. of molecules in ${}^{\prime }{V}^{\prime }$ litre
$=\frac{5.12\times V}{256}\times 6\times 10^{23}=1.2\times 10^{22}V$
Area covered $=\left(1.2\times 10^{22}V\times 0.2\times 10^{-14}\right)c{m}^2$
$=2.4\times 10^{7}Vc{m}^2$
$2.4\times 10^{7}V=480$
$V=2\times 10^{-5}litre$
$V=0.02ml$