Question

Write a balanced equation for each of the following combination reactions: (a) Nickel metal is heated with oxygen gas to produce nickel(II) oxide. (b) Iron wool is heated with oxygen gas to produce gray iron(III) oxide.

Short answer

(a) \( 2\text{Ni} + \text{O}_2 \rightarrow 2\text{NiO} \); (b) \( 4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 \).

Step-by-step solution

Identify Reactants and Products

For part (a), the reactants are nickel (Ni) and oxygen gas (O_2), and the product is nickel(II) oxide (NiO). For part (b), the reactants are iron (Fe) and oxygen gas (O_2), and the product is iron(III) oxide (Fe_2O_3).

Write Unbalanced Chemical Equations

Write down the chemical equations for the reactions based on the reactants and products identified. For (a): \( \text{Ni} + \text{O}_2 \rightarrow \text{NiO} \). For (b): \( \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3 \).

Balance Nickel Oxide Reaction

Balance the equation from step 2a by adjusting the coefficients. For the nickel and oxygen reaction: The balanced equation is \( 2\text{Ni} + \text{O}_2 \rightarrow 2\text{NiO} \). Check that there are equal numbers of each type of atom on both sides of the equation.

Balance Iron Oxide Reaction

Balance the equation from step 2b. For the iron and oxygen reaction, adjust coefficients: The balanced equation is \( 4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 \). Ensure there are equal numbers of each atom on both sides of the equation.

Verify Balancing

Check both equations to ensure each side has an equal number of each type of element. For part (a), there are 2 nickel and 2 oxygen atoms on both sides. For part (b), there are 4 iron and 6 oxygen atoms on both sides.

Key concepts

Combination Reactions

Combination reactions involve two or more reactants coming together to form a single product. This type of reaction is also known as a synthesis reaction. It commonly occurs with elements reacting to form a compound. In chemistry, these reactions help us understand how different substances can combine to create new materials.

For example, when nickel metal ( Ni) combines with oxygen gas ( O 2), they form nickel(II) oxide ( NiO), a new compound. Similarly, iron ( Fe) reacts with oxygen ( O 2) to produce iron(III) oxide ( Fe A2 3). These reactions are fundamental in fields like metallurgy, where metals are extracted or strengthened by combining them with other elements. Understanding combination reactions is essential for studying how materials form and behave.

Chemical Equation Balancing

Balancing chemical equations is a critical skill in chemistry. It ensures that the same number of atoms for each element are on both sides of the equation. This follows the law of conservation of mass, stating that matter cannot be created or destroyed in a chemical reaction.

To balance an equation, adjust the coefficients (the numbers before compounds) until each type of atom has the same amount on both sides:

• Start by writing down the unbalanced equation with correct formulas for reactants and products.
• Adjust the coefficients systematically, beginning with elements that appear in one compound first.
• Proceed to elements that are found in multiple compounds, balancing step-by-step.
• Double-check to ensure all atoms balance out on both sides.

As seen in the examples, nickel and oxygen's equation becomes balanced with 2 moles of Ni and O resulting in 2 moles of NiO, while the iron and oxygen equation balances with 4 moles of Fe and 3 moles of O yielding 2 moles of Fe 2O 3.

Reactants and Products Identification

In any chemical reaction, identifying the reactants and products is the first step. Reactants are substances that start a chemical reaction, while products are substances formed as a result of the reaction. This identification helps in understanding the transformation occurring during the reaction.

When dealing with combination reactions like the given exercise, you start by listing each substance involved:

• For nickel oxide, the reactants are nickel (Ni) and oxygen gas ( O 2), and the product is nickel(II) oxide (NiO).
• For iron(III) oxide, the reactants are iron (Fe) and oxygen gas ( O 2), and the product is iron(III) oxide ( Fe 2O 3).

This identification sets the stage for writing and balancing chemical equations, allowing us to visualize how atoms rearrange themselves to form new substances.

Stoichiometry

Stoichiometry involves using relationships from balanced chemical equations to calculate the quantities of reactants and products involved in a chemical reaction. It's an essential concept that allows chemists to predict the outcomes of reactions and plan accordingly.

In stoichiometry, the coefficients in a balanced equation tell us the proportion in which reactants combine and products form:

• The balanced equation for nickel oxide formation, \(2 ext{Ni} + ext{O}_2 ightarrow 2 ext{NiO}\), indicates two moles of nickel react with one mole of oxygen to produce two moles of nickel(II) oxide.
• For iron(III) oxide, \(4 ext{Fe} + 3 ext{O}_2 ightarrow 2 ext{Fe}_2 ext{O}_3\), four moles of iron react with three moles of oxygen to yield two moles of iron(III) oxide.

Understanding stoichiometry enables accurate scaling of reactions, crucial for industrial applications where precise amounts of materials are required to create desired products.