Problem 30 - Chemistry: Atoms First

Question

In a common experiment in the general chemistry laboratory, magnesium metal is heated in air to produce \(\mathrm{MgO} . \mathrm{MgO}\) is a white solid, but in these experiments it often looks gray, due to small amounts of \(\mathrm{Mg}_{3} \mathrm{N}_{2}, \mathrm{a}\) compound formed as some of the magnesium reacts with nitrogen. Write a balanced equation for each reaction.

Step-by-Step Solution

Answer

The balanced chemical equation for magnesium reacting with oxygen is \(2 Mg + O_2 \rightarrow 2 MgO\). For magnesium reacting with nitrogen, it is \(3 Mg + N_2 \rightarrow Mg_3N_2\).

Step 1: Write the Unbalanced Reaction for Magnesium and Oxygen

The reaction between magnesium metal and oxygen can be represented in unbalanced form as \[ Mg + O_2 \rightarrow MgO \] This equation shows magnesium reacting with oxygen to form magnesium oxide.

Step 2: Balance the Reaction of Magnesium and Oxygen

To balance the reaction, ensure that the number of atoms for each element is the same on both sides of the equation. The balanced equation is: \[ 2 Mg + O_2 \rightarrow 2 MgO \] Now, there are two magnesium atoms and two oxygen atoms on both sides of the equation.

Step 3: Write the Unbalanced Reaction for Magnesium and Nitrogen

The reaction between magnesium and nitrogen can be written in unbalanced form as: \[ Mg + N_2 \rightarrow Mg_3N_2 \] This shows magnesium reacting with nitrogen to form magnesium nitride.

Step 4: Balance the Reaction of Magnesium and Nitrogen

Balancing the magnesium and nitrogen reaction gives us: \[ 3 Mg + N_2 \rightarrow Mg_3N_2 \] There are now three magnesium atoms and two nitrogen atoms on both sides of the equation.

Key Concepts

Chemical Reaction

A chemical reaction involves the transformation of one or more substances into different substances. During this process, the atoms of the original substances rearrange themselves to form new molecules. One of the central principles in balancing chemical equations is the law of conservation of mass, which states that matter can neither be created nor destroyed in a chemical reaction.

For instance, when magnesium metal reacts with oxygen during burning, the atoms of magnesium and oxygen rearrange to form magnesium oxide, a new substance with different properties from the original elements. The key to understanding these reactions is to remember that the number of atoms for each element must remain the same before and after the reaction, ensuring that the equation is balanced.

In educational settings, envisioning a chemical reaction can be assisted by imagining how the elemental puzzle pieces come together to create new compounds. Providing a hands-on visual aid or using interactive simulations can enhance comprehension for students striving to grasp the delicate dance of atoms during chemical reactions.

Magnesium Oxide

Magnesium oxide, represented by the chemical formula \( MgO \), is a white solid commonly encountered in the laboratory. It's produced from the reaction of magnesium metal with oxygen, often during a combustion process. This simplicity in its chemical makeup, consisting of one magnesium atom and one oxygen atom, makes it an excellent example for understanding basic chemical bonding and stoichiometry in a chemistry course.

To push the concept further and aid in student understanding, the synthesis of magnesium oxide can be used to illustrate real-world applications such as its use as a refractory lining in furnaces or as a dietary supplement. This grounds the chemical principles in a practical context, thus improving engagement and retention. When presenting the balanced equation \( 2 Mg + O_2 \rightarrow 2 MgO \), highlighting the conservation of mass and the mole concept is key. It can be helpful to show how the coefficients in the equation demonstrate the ratio of moles of reactants used to moles of product formed.

Magnesium Nitride

Magnesium nitride, with the chemical formula \( Mg_3N_2 \), is a lesser-known compound than magnesium oxide but equally important to explore in the context of chemical education. It's formed when magnesium metal reacts with nitrogen, an abundant gas in the Earth's atmosphere, under high-temperature conditions.

This reaction can be particularly fascinating because it showcases a direct reaction between an active metal and an inert gas, which might initially seem counterintuitive to students. Understanding this chemical behavior is fundamental for comprehending more complex chemical synthesis. The balanced reaction \( 3 Mg + N_2 \rightarrow Mg_3N_2 \) demonstrates stoichiometry and proportional relationships between reactants and products. Employ dynamic demonstrations or molecular models to visually represent how the three magnesium atoms bond with two nitrogen atoms, forming the magnesium nitride compound. Such visual aids make the balancing process more understandable and emphasize the importance of achieving stoichiometric balance in chemical reactions.