Rectified spirit contains 95% ethanol by mass. The mole fraction of ethanol will be

Options

A. 0.881
B. 0.99
C. 0.118
D. 0.81

Answer

A

Explanation

95% ethanol `sol^(n)` means 95 g ethanol in 100 g sol., i.e., 5 g water
`X_(2)=n^(2)/(n_(2) + n_(1))=(W_(2)//M_(2))/((W_(2)//M_(2))+(W_(1)//M_(1)))`
`x_(2)=(95//46)/(95//46 + 5//18)=2.065/(2.065+0.278)=2.065/2.343=0.881`