Question

Write a balanced equation for the preparation of \(\mathrm{H}_{2}\) using (a) \(\mathrm{Mg}\) and an acid, (b) carbon and steam, (c) methane and steam.

Short answer

(a) \( \ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)} \) (b) \( \ce{C(s) + H2O(g) -> CO(g) + H2(g)} \) (c) \( \ce{CH4(g) + H2O(g) -> CO(g) + 3H2(g)} \)

Step-by-step solution

(a) Magnesium and an acid

The reaction of magnesium with an acid (such as hydrochloric acid, HCl) produces hydrogen gas and a salt (magnesium chloride, MgCl₂). The balanced equation for this reaction is: \( \ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)} \)

(b) Carbon and steam

The reaction of carbon with steam (water vapor) produces hydrogen gas and carbon monoxide (CO). The balanced equation for this reaction is: \( \ce{C(s) + H2O(g) -> CO(g) + H2(g)} \)

(c) Methane and steam

The reaction of methane with steam produces hydrogen gas and carbon monoxide (CO). The balanced equation for this reaction is: \( \ce{CH4(g) + H2O(g) -> CO(g) + 3H2(g)} \)

Key concepts

Balanced Chemical Equations

Chemical equations are used to represent chemical reactions. They show the substances present before the reaction, called reactants, and the substances formed by the reaction, known as products. A balanced chemical equation has equal numbers of each type of atom on both sides of the equation. This balance represents the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.
When balancing equations, you need to adjust the coefficients (the numbers placed before compounds or elements in the equation) so that the number of atoms for each element is the same on both sides. This ensures that the reaction accurately reflects the reality of how substances interact. Always begin by writing the unbalanced equation and then count the atoms of each element present in the reactants and products. Adjust the coefficients systematically until the equation is balanced.
For example, in the reaction between magnesium and hydrochloric acid, the unbalanced equation is \( \ce{Mg + HCl -> MgCl2 + H2} \). After counting the atoms and balancing, it becomes \( \ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)} \). Here, the number of magnesium, chlorine, and hydrogen atoms are equal on both sides.

Hydrogen Gas Production

Hydrogen gas is a colorless, odorless gas that can be produced by various chemical reactions. It is a major part of production processes in the industry, used in fuel cells and as a clean fuel source.
A common method of producing hydrogen gas involves the reaction of metals with acids. When metals such as magnesium interact with an acid like hydrochloric acid, hydrogen gas is released. The balanced equation for this reaction is \( \ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)} \). In this reaction, magnesium displaces hydrogen, and hydrogen gas is released as a byproduct.
Another significant method is steam reforming. This process involves reacting steam with hydrocarbons. For instance, when carbon reacts with steam, it forms carbon monoxide and hydrogen gas: \( \ce{C(s) + H2O(g) -> CO(g) + H2(g)} \). Similarly, methane can react with steam to produce hydrogen gas and carbon monoxide: \( \ce{CH4(g) + H2O(g) -> CO(g) + 3H2(g)} \). These reactions are crucial for producing hydrogen on a large scale.

Inorganic Chemistry

Inorganic chemistry focuses on compounds that are not primarily based on carbon, which distinguishes it from organic chemistry. It covers a broad range of substances including metals, minerals, and organometallic compounds.
Within inorganic chemistry, reactions involving elements like magnesium and carbon with various compounds are common. For example, magnesium's reaction with hydrochloric acid to form hydrogen gas and magnesium chloride is a typical inorganic process. This reaction showcases the interaction between a metal and an acid, leading to the formation of ionic compounds, which is a key concept in inorganic chemistry.
Other reactions like the combination of carbon and steam or methane and steam belong to this branch of chemistry as well. They demonstrate the principles of reactivity and catalysis, which are vital in industrial applications. Understanding these processes allows chemists to manipulate reactions for desired outcomes, advancing fields such as material science and catalysis. Inorganic chemistry also plays a critical role in the development of new materials and the study of elements and their compounds.