Question

Hydrogen gas is not obtained when zinc reacts with
A.Cold water
B.${H_2}S{O_4}$
C.$Dil.HCl$
D.Hot $20\% NaOH$ solution

Answer 1

We need to know that zinc is a chemical element with the symbol $Zn$ and atomic number $30$. Zinc is a slightly brittle metal at room temperature and has a silvery-grayish appearance when oxidation is removed. It is the first element in the group $12$ of the periodic table. In some respects, zinc is chemically similar to magnesium.

Complete answer:
We need to remember that zinc is a low reactive metal which does not react with cold water and hence no gas is evolved.
We will look at all the options one by one. In the question it is asked which of the following does not react with zinc metal to liberate hydrogen gas.
Option A) this option is correct as cold water does not react with zinc metal to liberate hydrogen gas. In this reaction no product is formed or you can say the reaction cannot proceed.
$Zn + {H_2}O \to No \, reaction$
Option B) This option is incorrect as hydrogen gas is liberated by reacting sulfuric acid with zinc metal. The reaction can be represented as:
$Zn + {H_2}S{O_4} \to ZnS{O_4} + {H_2}$
Option C) this option is incorrect as hydrogen gas is liberated by reacting hydrochloric acid with zinc metal. The reaction can be represented as:
$Zn + 2HCl \to ZnC{l_2} + {H_2}$
Option D) this option is incorrect as hydrogen gas is liberated by reacting hot sodium hydroxide solution with zinc metal. The reaction can be represented as:
$Zn + 2NaOH \to N{a_2}Zn{O_2} + {H_2}$

Option A is the correct answer.

Note:
We have to know that many alloys contain zinc, including brass. Other metals long known to form binary alloys with zincare aluminium, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium, and sodium. Although neither zinc nor zirconium is ferromagnetic, their alloy $ZrZ{n_2}$ exhibits ferromagnetism below $35K$.