Question

Which metal is preferred for collecting hydrogen from hot water? Write the balanced equation for each case.

Answer 1

Hint: Hydrogen is a very abundant element and is formed as a by – product in a variety of reactions. The hydrogen formed in these reactions is usually in the gaseous form. Because of this it gets kind of difficult to collect hydrogen gas in these cases, while collecting the desired product from the same reaction. hence there are different methods used to collect and obtain hydrogen gas.
Complete Step-by-Step Answer:
Before we move forward with the solution of this question, let us first understand some important basic concepts.
One of the biggest natural sources of hydrogen is water. Water has two atoms of hydrogen and one atom of oxygen. Water can be decomposed to form elemental hydrogen. But to do this, we must need strong reagents that can break the bonds between the hydrogen atoms and the oxygen atoms.
If the reagents used are highly reactive metals like potassium or sodium, then no other external stimulus is required for proceeding with the decomposition reaction. These metals react violently with water and release hydrogen gas along with the formation of their corresponding oxides. These reactions can take place at either room temperature or even at slightly colder temperatures.
On the other hand, lesser reactive metals need some external stimulus to make the reaction proceed in the forward direction. To do this, we can use hot water to provide some extra energy necessary to break the O – H bonds in water. To carry out these types of reactions, we can use less reactive metals like zinc, magnesium or aluminium. The chemical equations for these reactions can be given as:
\[Zn + 2{H_2}O \to ZnO + {H_2}\]
\[Mg + {H_2}O \to MgO + {H_2}\]
\[2Al + 3{H_2}O \to A{l_2}{O_3} + {H_2}\]
Note: Some metals have reactivities which are lower than metals like zinc, aluminium or magnesium. Such metals can be reacted with steam to decompose the water molecules. The extremely high temperature of the steam helps enable this process. These low reactivity metals include iron, tin, nickel, etc.