Question

When magnesium burns in air, it forms both an oxide and a nitride. Write balanced equations for the formation of both compounds.

Short answer

Mg + O₂ → MgO: 2Mg + O₂ → 2MgO; Mg + N₂ → Mg₃N₂: 3Mg + N₂ → Mg₃N₂.

Step-by-step solution

Identify Reactants and Products

When magnesium burns in air, it reacts with oxygen to form magnesium oxide and with nitrogen to form magnesium nitride. The reactants are magnesium (Mg) and the components of air, which include oxygen (O₂) and nitrogen (N₂). The products are magnesium oxide (MgO) and magnesium nitride (Mg₃N₂).

Write Equation for Magnesium Oxide Formation

Magnesium reacts with oxygen to form magnesium oxide. Write the unbalanced equation for this reaction: \[ \text{Mg} + \text{O}_2 \rightarrow \text{MgO} \]

Balance Magnesium Oxide Equation

Balance the equation by making sure there are equal numbers of each type of atom on both sides. In MgO, oxygen appears as a diatomic molecule O₂, so two MgO molecules are required to balance the oxygen:\[ 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \]

Write Equation for Magnesium Nitride Formation

Magnesium also reacts with nitrogen to form magnesium nitride. Write the unbalanced equation: \[ \text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2 \]

Balance Magnesium Nitride Equation

Balance the equation by making sure there are equal numbers of each type of atom on both sides. For Mg₃N₂, you need three Mg atoms and two N molecules:\[ 3\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2 \]

Key concepts

Balancing Chemical Equations

Balancing chemical equations might seem complex at first, but it's all about ensuring the same number of each atom on both sides of the equation. This reflects the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. This means:

• All atoms present in the reactants must be accounted for in the products.
• Coefficients are used to balance the number of atoms. These are the numbers placed before the chemical formulas. They indicate how many molecules or moles of that substance participate in the reaction.

Balancing requires us to adjust these coefficients until we have the same number of each type of atom on both sides.
For example, in the creation of magnesium oxide, we start with the unbalanced equation \[\text{Mg} + \text{O}_2 \rightarrow \text{MgO}\]To balance it, we see one oxygen atom in each molecule of magnesium oxide, but \(O_2\) means oxygen comes in pairs. Thus, we need two \(\text{MgO}\) for every \(\text{O}_2\). This leads us to:\[2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}\]Similarly, balancing magnesium nitride involves recognizing that three magnesium atoms are needed for every single molecule of \(\text{Mg}_3\text{N}_2\). This careful balancing allows chemists to predict the quantities of reactants needed and products formed.

Magnesium Oxide

Magnesium oxide, or \(\text{MgO}\), is a simple yet important compound formed from magnesium when it burns in air. Magnesium is a highly reactive metal and readily combines with oxygen to produce this compound.
Here’s what you need to know about this process:

• Magnesium reacts with oxygen (\(\text{O}_2\)), which is a diatomic molecule, meaning it naturally occurs in a pair of atoms in nature.
• The reaction is a direct combination, resulting in a single product, magnesium oxide.
• To write the equation: \(\text{Mg} + \text{O}_2 \rightarrow \text{MgO}\)

To balance the equation, notice that \(\text{O}_2\) provides two oxygen atoms while \(\text{MgO}\) contains one per molecule. The balanced equation is:\[2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}\]This exothermic reaction releases a bright white light and results in a stable compound used in a variety of applications, including fireproofing and medicine due to its high melting point and alkaline nature.

Magnesium Nitride

Magnesium nitride \(\text{Mg}_3\text{N}_2\) formation is a lesser-known yet crucial reaction when magnesium burns in air, especially at high temperatures. While it might not be as common as magnesium oxide, the formation of magnesium nitride still follows the same chemical principles of reaction.

• Magnesium reacts with nitrogen (\(\text{N}_2\)), another diatomic molecule present in the air.
• Nitrogen is relatively inert, but under suitable high-temperature conditions, it combines with magnesium.
• The unbalanced reaction starts as \(\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2\).

Balancing this equation involves understanding:

• Each molecule of \(\text{Mg}_3\text{N}_2\) needs three \(\text{Mg}\) atoms.
• \(\text{N}_2\) requires two nitrogen atoms.

The fully balanced equation is:\[3\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2\]Magnesium nitride has its uses, often in materials science and the production of specialty chemicals. The careful balancing of atoms in this reaction satisfies the conservation of mass, ensuring a correct depiction of the chemical change.