Question

When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.

Answer 1

Hydrogenation: The process of adding hydrogen to the liquid fat to make it solid at room temperature is called hydrogenation. For example, margarine, mineral turpentine, and aniline.

Dilute solution: A dilute solution is one in which there is a relatively small amount of solute dissolved in the solution. For example, dilute Hydrochloric acid$\left(\mathrm{HCl}\right)$ and dilute Sulphuric acid$\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$.

Displacement reaction: A chemical reaction in which a more reactive element displaces less reactive element from its compound is called a displacement reaction.

When zinc reacts with a dilute solution of a strong acid like hydrochloric acid$\left(\mathrm{HCl}\right)$, it gives zinc chloride and hydrogen gas. Because zinc is more reactive than hydrogen it displaces hydrogen from its salt solution. The chemical reaction involved in it is shown below:

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{l}\right)}\to \underset{\mathrm{Zinc}\mathrm{chloride}}{{\mathrm{ZnCl}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

In the above reaction, the only Hydrogen gas is evolved that is used in the hydrogenation process also. Therefore, the gas evolved in the chemical reaction of zinc and the dilute solution of a strong acid is Hydrogen$\left({\mathrm{H}}_2\right)$.

Hydrogenation of Ethene$\left({\mathrm{C}}_2{\mathrm{H}}_4\right)$ involves the addition of two hydrogen atoms to the double bond of Ethene, resulting in the formation of saturated Ethene. The chemical reaction of the Hydrogenation process is shown below:

$\underset{\left(\mathrm{methylene}\right)}{{\mathrm{CH}}_2\left(\mathrm{l}\right)}=\underset{\left(\mathrm{methylene}\right)}{{\mathrm{CH}}_2\left(\mathrm{l}\right)}+\underset{\left(\mathrm{Hydrogen}\right)}{{\mathrm{H}}_2\left(\mathrm{g}\right)}\stackrel{\mathrm{Hydrogenation}}{\to }\underset{\left(\mathrm{ethane}\right)}{{\mathrm{CH}}_3{\mathrm{CH}}_3\left(\mathrm{s}\right)}$

Test to detect gas: A lit match is brought near the mouth of the test tube to detect the gas. If the gas burns with a pop sound, it confirms the presence of hydrogen gas.

Final answer: The gas evolved in the reaction of Zinc with a dilute solution of a strong acid is Hydrogen gas that is used in the hydrogenation process.