Question

Write a balanced equation for each of the following combination reactions: (a) Carbon is heated with oxygen to give carbon monoxide gas. (b) Phosphorus is heated with oxygen to give solid diphosphorus pentaoxide.

Short answer

(a) 2C + O_2 → 2CO. (b) 4P + 5O_2 → 2P_2O_5.

Step-by-step solution

Identify Reactants and Products

For (a), the reactants are carbon (C) and oxygen (O_2) and the product is carbon monoxide (CO). For (b), the reactants are phosphorus (P) and oxygen (O_2) and the product is diphosphorus pentaoxide (P_2O_5).

Write Initial Word Equations

For (a), the word equation is: Carbon + Oxygen → Carbon monoxide. For (b), the word equation is: Phosphorus + Oxygen → Diphosphorus pentaoxide.

Write Chemical Formulas for Each Substance

Convert the word equations to chemical formulas. For (a), the formula is: C + O_2 → CO. For (b), the formula is: P + O_2 → P_2O_5.

Balance Each Equation

For (a), starting with C + O_2 → CO, balance the equation: The equation is not balanced because on the reactant side there are 2 oxygen atoms while only 1 oxygen atom is present on the product side. The balanced equation is 2C + O_2 → 2CO. For (b), starting with P + O_2 → P_2O_5: The equation is not balanced because the reactants have 1 phosphorus atom and 2 oxygen atoms while the product has 2 phosphorus atoms and 5 oxygen atoms. The balanced equation is 4P + 5O_2 → 2P_2O_5.

Key concepts

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the conservation of mass. It involves making sure that the number of atoms for each element is the same on both sides of the equation. This adherence to the law means that what goes into a reaction comes out, just rearranged. To balance a chemical equation:

• First, write down the unbalanced equation with reactants on the left and products on the right.
• Adjust coefficients, which are numbers placed before compounds, not subscripts (numbers within the formulas), to ensure each side has the same number of atoms for each element.
• Always check your balanced equation by counting the atoms of each element on both sides to ensure they match.

In our examples: - For the reaction of carbon and oxygen to form carbon monoxide (CO), we start with C + O${}_2$ → CO and notice that the oxygen atoms are unbalanced. The correct balance is achieved with 2C + O${}_2$ → 2CO.- For phosphorus and oxygen forming diphosphorus pentaoxide (P${}_2$O${}_5$), we start with P + O${}_2$ → P${}_2$O${}_5$. Balancing this involves adjusting to 4P + 5O${}_2$ → 2P${}_2$O${}_5$.
Balancing equations demands practice and patience, focusing on one type of atom at a time.

Combination Reactions

Combination reactions, also referred to as synthesis reactions, are a type of chemical reaction where two or more substances combine to form a single product. They are generally straightforward, involving elements or simpler compounds merging to create a more complex compound. These types of reactions often require energy in the form of heat.A typical example is the reaction between carbon and oxygen. When carbon (C) is heated in the presence of oxygen (O${}_2$), they combine to form carbon monoxide (CO), as shown: C + O${}_2$ → CO.
Similarly, phosphorus (P) reacts with oxygen (O${}_2$) to form diphosphorus pentaoxide (P${}_2$O${}_5$) in the reaction:P + O${}_2$ → P${}_2$O${}_5$.In industry and the environment, combination reactions are crucial. They are widely used in forming new compounds and materials. Understanding combination reactions helps predict the outcomes of chemical processes, which is vital for fields ranging from manufacturing to environmental science.

Chemical Formulas

Chemical formulas are symbolic representations of chemical compounds and are essential for conveying detailed information about substances in chemistry. They consist of elements’ chemical symbols and numerical subscripts that indicate the number of each type of atom within a molecule.The formula for a molecule of water, for example, is H${}_2$O, indicating it contains two hydrogen atoms and one oxygen atom. For the exercises here:- The chemical formula for carbon monoxide is CO, meaning it is composed of one carbon and one oxygen atom.- Diphosphorus pentaoxide is represented by P${}_2$O${}_5$, showing it has two phosphorus and five oxygen atoms.These formulas are not just mere representations but are an essential part of writing and balancing chemical equations. They allow us to visualize and balance the elements involved in chemical reactions. Understanding and using chemical formulas accurately is critical in tracking chemical changes and predicting new substances.