Which of the following is commonly employed for removing water from ethanol ?

Options

A. `Na`
B. `H_(2)SO_(4)`
C. `CaCl_(2)`
D. `CaO`

Answer

D

Explanation

`C_(2)H_(5)OH + Na rarr C_(2)H_(5)overset(-)ONa^(+) + (1)/(2)H_(2)`
When ethyl alcohol is treated with concentrated sulphuric acid , the ester ethyl hydrogen sulphate , `C_(2)H_(5)HSO_(4)`, is formed .
`CH_(3)CH_(2)O-H+HO-SO_(2)-OHrarrCH_(3)CH_(2)OSO_(2)OH+H_(2)O`
If excess of alcohol is present, ester reacts forming diethyl ether : `CH_(3)CH_(2)OSO_(2)OH + CH_(3)CH_(2)OH rarr CH_(3)CH_(2)OCH_(2)CH_(3) + H_(2)SO_(4)`
If the sulphuric acid is in excess and the temperature is raised above `170^(@)C` , the ester decomposes yielding ethylene:
`CH_(3)CH_(2)OSO_(2)OH rarr C_(2)H_(4) + H_(2)SO_(4)`
Ethanol cannot be dried by means of calcium chloride , since a compound (an alcoholate) is formed , `CaCl_(2).3C_(2)H_(5)OH`.Distillation of rectified spirit over calcium oxide , and then over calcium , gives absolute alcohol.