Question

When solid red phosphorus, \(P_{4}\), is burned in air, the phosphorus combines with oxygen, producing a choking cloud of tetraphosphorus decoxide. Write the unbalanced chemical equation for this reaction.

Short answer

The unbalanced chemical equation for the reaction between red phosphorus and oxygen is: \(P_{4} + O_{2} \rightarrow P_{4}O_{10}\).

Step-by-step solution

Write the chemical formulas of the reactants and products:

We know that red phosphorus (\(P_{4}\)) reacts with oxygen (O\(_{2}\)) in the air to form tetraphosphorus decoxide (\(P_{4}O_{10}\)). Now that we have the chemical formulas of the reactants and the product, we can write the unbalanced chemical equation.

Write the unbalanced chemical equation:

To write the unbalanced chemical equation, we need to place the reactants on the left side with an arrow pointing towards the products on the right side. The unbalanced chemical equation is: \[P_{4} + O_{2} \rightarrow P_{4}O_{10}\] This equation shows that red phosphorus and oxygen react to form tetraphosphorus decoxide.

Key concepts

Unbalanced Chemical Equation

An unbalanced chemical equation is the starting point for representing a chemical reaction in scientific terms. It shows which substances are involved in a reaction, indicating the reactants and the products but does not yet reflect the conservation of mass. This is because it does not account for the principle that matter cannot be created or destroyed. Instead, it provides the basic framework, which chemists use to visualize the transformation.

In this case, the initial unbalanced equation for the reaction between red phosphorus and oxygen is:

• Reactants: Red phosphorus (\(P_4\)) and oxygen gas (\(O_2\))
• Product: Tetraphosphorus decoxide (\(P_4O_{10}\))
• Unbalanced Equation: \[P_4 + O_2 \rightarrow P_4O_{10}\]

This simple framework doesn't reflect the balanced distribution of oxygen atoms, which is crucial for satisfying the law of conservation of mass.

Red Phosphorus

Red phosphorus is an allotrope of phosphorus, meaning it exists in several different forms. It is a stable, non-toxic form of phosphorus that is commonly encountered. Unlike its more reactive counterpart, white phosphorus, red phosphorus is relatively safe and is often used in safety matches, fireworks, and in laboratory settings for various chemical reactions.

Characteristics of red phosphorus include:

• Appearance: Dark red color;
• Stability: More stable than white phosphorus;
• Toxicity: Relatively non-toxic compared to other forms of phosphorus;
• Reactivity: Combines with oxygen when heated, forming phosphorus oxides.

In the given reaction, red phosphorus (\(P_4\)) serves as a reactant that reacts with oxygen in the air to form a new compound, tetraphosphorus decoxide.

Tetraphosphorus Decoxide

Tetraphosphorus decoxide, chemically denoted as \(P_4O_{10}\), is the product formed when phosphorus reacts with oxygen. This compound is a phosphorous oxide and is significant for its role as a robust desiccant due to its ability to absorb water from the air.

Key points about tetraphosphorus decoxide:

• Formula: \(P_4O_{10}\)
• Structure: Composed of four phosphorus atoms and ten oxygen atoms
• Use: Commonly used as a drying agent because of its high affinity for water
• Formation: Produced from the oxidation of phosphorus, often resulting in a white crystalline or powdery substance

During the chemical reaction discussed here, red phosphorus burns in the presence of oxygen to produce this compound, emitting a characteristic white smoke as a visual indicator of its development.