Question

Complete and balance each of the following combination reactions: (a) \(\mathrm{Na}+\mathrm{I}_{2} \rightarrow\) (b) \(\mathrm{Ba}+\mathrm{N}_{2} \rightarrow\)

Short answer

Reaction (a): \(2\mathrm{Na} + \mathrm{I}_2 \rightarrow 2\mathrm{NaI}\); Reaction (b): \(3\mathrm{Ba} + \mathrm{N}_2 \rightarrow \mathrm{Ba_3N_2}\).

Step-by-step solution

Identify Reaction Type

Both reactions are combination reactions, where two or more substances combine to form a single compound.

Write Unbalanced Chemical Equations

For reaction (a), the formula is \ \(\mathrm{Na} + \mathrm{I}_2 \rightarrow \mathrm{NaI}\)\. For reaction (b), it is \ \(\mathrm{Ba} + \mathrm{N}_2 \rightarrow \mathrm{Ba_3N_2}\)\. The products are determined by the common ionic charges: Na forms \(\mathrm{Na^+}\) and I forms \(\mathrm{I^-}\); Ba forms \(\mathrm{Ba^{2+}}\) and N forms \(\mathrm{N^{3-}}\).

Balance Equation for Reaction (a)

The unbalanced equation is \(\mathrm{Na} + \mathrm{I}_2 \rightarrow \mathrm{NaI}\). Since iodide is a diatomic molecule, we need 2 sodium atoms to balance one iodine molecule. Thus, the balanced equation is \(2\mathrm{Na} + \mathrm{I}_2 \rightarrow 2\mathrm{NaI}\).

Balance Equation for Reaction (b)

The unbalanced equation is \(\mathrm{Ba} + \mathrm{N}_2 \rightarrow \mathrm{Ba_3N_2}\). Balancing barium and nitrogen, we find that 3 Ba atoms and 1 \(\mathrm{N_2}\) molecule are needed, giving the balanced equation \(3\mathrm{Ba} + \mathrm{N}_2 \rightarrow \mathrm{Ba_3N_2}\).

Key concepts

Combination Reactions

Combination reactions are a fundamental type of chemical reaction in which two or more reactants unite to form a single product. These reactions are easy to identify because the equation starts with multiple separate substances and results in a sole compound. Combination reactions are also known as synthesis reactions, aligning with the concept of synthesizing a new product.
In general, combination reactions involve elements that readily combine due to their chemical properties. For example, metals often react with nonmetals to form ionic compounds, where the resulting product showcases traits from both initial reactants. Such reactions are visibly characterized by energy changes, either releasing or absorbing energy, thus often resulting in noticeable changes like light or heat.
Understanding combination reactions offers a window into how substances interact chemically, forming the basis for larger scale chemical processes critical to both industrial applications and natural phenomena.

Balancing Chemical Equations

Balancing chemical equations is an essential skill in chemistry to ensure that a chemical reaction obeys the law of conservation of mass. This law states that matter cannot be created or destroyed in a chemical reaction. Thus, the quantity of each element must remain constant before and after the reaction.
To balance an equation, you must ensure that the number of each type of atom is the same on both sides of the equation. If we consider the reaction \(\mathrm{Na} + \mathrm{I}_2 \rightarrow \mathrm{NaI}\), initially, the equation is unbalanced because we have two iodine atoms on the reactant side but one on the product side. Balancing involves making them equal, so we adjust coefficients, resulting in \(2\mathrm{Na} + \mathrm{I}_2 \rightarrow 2\mathrm{NaI}\).
This process is systematic and often involves trial and error, requiring practice and patience. A balanced equation provides vital information about the proportions of reactants and products, which is necessary for calculations in stoichiometry.

Ionic Compounds

Ionic compounds are formed as a result of the combination reactions between metals and nonmetals. These compounds consist of positively charged ions, called cations, and negatively charged ions, called anions. The overall charge remains neutral, as the ions balance each other's charges.
In the case of sodium (\(\mathrm{Na^+}\)) and iodine (\(\mathrm{I^-}\)), the formation of sodium iodide (\(\mathrm{NaI}\)) is a classic example of an ionic compound. Likewise, barium (\(\mathrm{Ba^{2+}\)) and nitrogen (\(\mathrm{N^{3-}\)) combine to form barium nitride (\(\mathrm{Ba_3N_2}\)), balancing their charges in the compound.
Understanding ionic compounds involves recognizing the electron transfer between atoms, typically with metals losing electrons and nonmetals gaining them. This electron transfer leads to the stability of the compound due to the electrostatic attractions between oppositely charged ions. Ionic compounds are crucial in numerous applications, from their role in biological systems to their use in industrial manufacturing.