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.NCERT Class XScience - Exemplar ProblemsChapter_Acids, Bases and Salts

Answer 1

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When we treat a metal with acid the release of Hydrogen takes place.
But this gas is also used in hydrogenation of oil. The complete equation can be written as

Zn + 2HCl ----------> ZnCl2 + H2

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Answer 2

Answer: Hydrogen gas.

$Zn+2HCl\rightarrow ZnCl_2+H_2$

It burns with a pop sound when a match stick is brought near the gas.

Explanation: When Zinc is treated with a strong acid such as $HCl$, zinc being more reactive than hydrogen displaces hydrogen from its salt solution and thus produce zinc chloride and hydrogen gas.

$Zn+2HCl\rightarrow ZnCl_2+H_2$

This is a single replacement reaction as more reactive zinc displaces hydrogen. The hydrogen is used for hydrogenation of oils to convert vegetable oils to vanaspati ghee.

$CH_2=CH_2+H_2\xrightarrow[]{hydrogenation} CH_3CH_3$

The hydrogen gas is odorless and colorless and burns with a pop sound when a burning match stick is brought near it.