Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040 (assume the density of water to be one). Use the data given in the following table to calculate the molar mass of naturally occuring argon isotopes :

Explanation

(a) Mole fraction of ethanol = 0.04
`0.04=n_(2)/(n_(1)+n_(2))`
Moles of ethanol `n_(1)` = 0.04
No. of moles of water = 1 - 0.04 = 0.996
Wt. of water = `0.996xx18` gm
Vol. of water = `0.996xx18` ml.
Molarity of ethanol = `("No. of moles")/("Vol. of water in lit.")`
`=(0.04xx1000)/(0.996xx18)=2.223M`
(b) Molar mass of Argon
`=((35.96755xx0.337)+(37.96272xx0.063)+(39.9624xx99.6))/100`
= 39.947