Question

When elemental phosphorus, \(\mathrm{P}_{4},\) burns in oxygen gas, it produces an intensely bright light, a great deal of heat, and massive clouds of white solid phosphorus(V) oxide \(\left(\mathrm{P}_{2} \mathrm{O}_{5}\right)\) product. Given these properties, it is not surprising that phosphorus has been used to manufacture incendiary bombs for warfare. Write the unbalanced equation for the reaction of phosphorus with oxygen gas to produce phosphorus(V) oxide.

Short answer

The balanced chemical equation for the reaction between phosphorus (P₄) and oxygen gas (O₂) to produce phosphorus(V) oxide (P₂O₅) is: \(P_{4} + 5 O_{2} \rightarrow 2 P_{2}O_{5}\)

Step-by-step solution

Write the reactants and products in a chemical equation

To write the unbalanced chemical equation, we first represent the reactants (P₄ and O₂) on the left side of the equation, and the product (P₂O₅) on the right side, separated by an arrow. The equation is not yet balanced, so we will need to determine the correct coefficients to ensure the number of atoms of each element is equal on both sides. P₄ + O₂ → P₂O₅

Balance the chemical equation

To balance the chemical equation, we need to find the coefficients so that the number of atoms of each element is conserved. When balancing the equation, start with elements that appear in only one molecule on each side, in this case, phosphorus. There are 4 phosphorus atoms in the reactants (P₄) and 2 phosphorus atoms in the products (P₂O₅). To balance the phosphorus atoms, we multiply P₂O₅ by a coefficient of 2: P₄ + O₂ → 2 P₂O₅ Next, we balance the oxygen atoms. There are 2 oxygen atoms in O₂ and 10 oxygen atoms in the products ((2 × 5) in 2 P₂O₅). To balance the oxygen atoms, we can multiply O₂ by a coefficient of 5: P₄ + 5 O₂ → 2 P₂O₅ Now the chemical equation is balanced: P₄ + 5 O₂ → 2 P₂O₅

Key concepts

Balancing Chemical Equations

Balancing chemical equations is crucial in chemistry. It ensures that the law of conservation of mass is followed, meaning that the number of each kind of atom is equal on both sides of the equation.
To balance a chemical equation, start by identifying all the reactants and products involved. In the unbalanced reaction of phosphorus with oxygen, we write:

• Reactants: Phosphorus ( \( \text{P}_4 \) ) and Oxygen ( \( \text{O}_2 \) )
• Products: Phosphorus(V) oxide ( \( \text{P}_2\text{O}_5 \) )

To achieve balance, adjust coefficients to ensure the number of atoms on both the reactant and product sides are the same.
Begin with elements that are isolated in one reactant and one product, making it easier to adjust their coefficients while minimizing disturbance to others. As we solve, remember that changes in coefficients affect the entire molecule. Balancing requires practice but becomes intuitive over time.

Reactants and Products

In any chemical reaction, it's essential to understand the roles of reactants and products.
Reactants are the starting substances in a chemical reaction, while products are the substances formed as a result. Let's break it down:

• Reactants: In the phosphorus and oxygen reaction, we start with phosphorus ( \( \text{P}_4 \) ) and oxygen gas ( \( \text{O}_2 \) ). Reactants are always written on the left side of the equation, leading to the process of the reaction.
• Products: In this reaction, phosphorus(V) oxide ( \( \text{P}_2\text{O}_5 \) ) appears as the product. It is the outcome and housed on the right side of the equation.

This simple understanding of reactants and products helps predict how elements combine and transform.
It is a fundamental skill for interpreting and solving chemical equations. Highlight the transformation by using an arrow (\( \rightarrow \)) to show the direction of the reaction from reactants to products.

Phosphorus Reactions

Phosphorus, a non-metal with fascinating properties, is reactive and plays a major role in many chemical reactions. In its elemental form, phosphorus appears in a variety of allotropes, including white and red phosphorus.
White phosphorus is highly reactive and is the specific allotrope involved in the reaction with oxygen gas to form phosphorus(V) oxide ( \( \text{P}_2\text{O}_5 \) ).
When burned, it releases significant amounts of energy, manifesting as bright light and heat. This attribute makes such reactions visually dramatic and exothermic.During the reaction:

• The strong affinity of phosphorus for oxygen leads to rapid oxidation.
• Massive white clouds form, often associated with explosive characteristics, believed to have historical military applications.

Understanding phosphorus reactions, especially with oxygen, offers insight into why careful handling and specific controlled conditions are necessary for safety and accuracy in experiments. These phosphorus reactions demonstrate both the beauty and potential hazards inherent in exothermic reactions.