Question

To remove the last traces of water from alcohol, the metal used is
A. Sodium
B. Potassium
C. Calcium
D. Aluminium

Answer 1

Hint: In the preparation of alcohol, the solution is condensed to discard residual water. Additional traces of water can be removed by using a metal which can readily react with water.

Complete Step by Step Solution:
Ethanol or ethyl alcohol is an organic chemical compound. It is an ethyl group attached to the oxygen of the hydroxyl group. It is a volatile liquid. It is the simplest alcohol and is the component of alcoholic beverages.

Ethanol is manufactured by the hydration of ethene through biological methods i.e., by fermenting sugars with yeast. Water and ethanol are produced in this method. During this preparation of alcohol, water, and other impurities are discarded from the solution by various processes.

The solution undergoes fractional distillation or condensation to discard water. But still, little water is left which is removed by the use of metal. This metal must not harm the alcohol in any way. This metal is calcium.

We know that calcium is an alkaline earth metal that reacts with water to form calcium hydroxide. It is an inorganic compound and is a colourless crystal or white powder. So, water by reacting with calcium forms calcium hydroxide which is a solid crystal and is eliminated from the solution leaving only the ethanol behind.
So, option C is correct.

Note: Sodium metal can also be used in this process which will form sodium hydroxide. But sodium metal reacts readily with ethanol and forms sodium ethoxide and liberates hydrogen gas. So, ethanol will get consumed in this process. Hence, using sodium metal to remove the water is avoided.