Production of Hydrogen: Reactions and Examples

Production of Hydrogen

Introduction

Hydrogen gas (H2) is an important chemical element produced by several types of chemical reactions. Understanding these reactions is essential for general chemistry, especially in the context of chemical equations and reactivity.

H2 from Ionic Hydrides

Ionic hydrides are compounds formed between hydrogen and highly electropositive metals (usually Group 1 or Group 2 elements). When these hydrides react with water, they produce hydrogen gas.

• Key Reaction: Metal hydride reacts with water to form metal hydroxide and hydrogen gas.

General Equation:

$\text{MH}_2 (s) + 2\text{H}_2\text{O} (l) \rightarrow 2\text{H}_2 (g) + \text{M(OH)}_2 (aq)$

• Example: Lithium hydride reacts with water:

$\text{LiH} (s) + \text{H}_2\text{O} (l) \rightarrow \text{LiOH} (aq) + \text{H}_2 (g)$

H2 from Metal & Acid

Many metals react with acids to produce hydrogen gas. This is a classic single displacement reaction where the metal replaces hydrogen in the acid, forming a salt and releasing hydrogen gas.

• Key Reaction: Metal reacts with acid to form salt and hydrogen gas.

General Equation:

$\text{M} (s) + 2\text{H}^+ (aq) \rightarrow \text{M}^{2+} (aq) + \text{H}_2 (g)$

• Example: Aluminum reacts with hydrochloric acid:

$\text{Al} (s) + \text{HCl} (aq) \rightarrow \text{AlCl}_3 (aq) + \text{H}_2 (g)$

Practice Problems

• Practice 1: Complete and balance the reaction of barium hydride with water.

$\text{BaH}_2 (s) + \text{H}_2\text{O} (l) \rightarrow \text{Ba(OH)}_2 (aq) + \text{H}_2 (g)$

• Practice 2: Complete and balance the reaction of zinc with sulfuric acid.

$\text{Zn} (s) + \text{H}_2\text{SO}_4 (aq) \rightarrow \text{ZnSO}_4 (aq) + \text{H}_2 (g)$

Summary Table: Methods of Hydrogen Production

Method	Reactants	Products	Example Equation
From Ionic Hydrides	Metal hydride + Water	Metal hydroxide + Hydrogen gas	$\text{LiH} (s) + \text{H}_2\text{O} (l) \rightarrow \text{LiOH} (aq) + \text{H}_2 (g)$
From Metal & Acid	Metal + Acid	Salt + Hydrogen gas	$\text{Zn} (s) + \text{H}_2\text{SO}_4 (aq) \rightarrow \text{ZnSO}_4 (aq) + \text{H}_2 (g)$

Key Concepts

• Hydrogen gas can be produced by reacting ionic hydrides with water or metals with acids.

• Balancing chemical equations is essential to accurately represent these reactions.

• These reactions are examples of single displacement and hydrolysis processes in chemistry.