Question

Complete and balance the equation for each of the following combination reactions. (a) \(\mathrm{Ca}(s)+\mathrm{N}_{2}(g) \longrightarrow\) (b) \(\mathrm{K}(s)+\mathrm{Br}_{2}(l)\) (c) \(\mathrm{Al}(s)+\mathrm{O}_{2}(g)\)

Short answer

The made equations are: \n(a) \(\mathrm{3Ca}(s) + \mathrm{N}_{2}(g) \longrightarrow \mathrm{Ca}_3\mathrm{N}_{2}(s)\) \n(b) \(\mathrm{2K}(s) + \mathrm{Br}_{2}(l) \longrightarrow \mathrm{2KBr}(s)\) \n(c) \(\mathrm{4Al}(s) + \mathrm{3O}_{2}(g) \longrightarrow \mathrm{2Al}_{2}\mathrm{O}_{3}(s)\)

Step-by-step solution

Identify the Reactions

The first stage requires identifying the substances that are undergoing reactions. In these cases, we have: (a) Calcium (\(\mathrm{Ca}\)) and Nitrogen Gas (\(\mathrm{N}_{2}\))(b) Potassium (\(\mathrm{K}\)) and Bromine (\(\mathrm{Br}_{2}\))(c) Aluminum (\(\mathrm{Al}\)) and Oxygen Gas (\(\mathrm{O}_{2}\))

Predict the Products

The second step involves predicting the products of the reactions. (a) Calcium and Nitrogen combine together to form Calcium Nitride. The completed equation would be \(\mathrm{Ca} + \mathrm{N}_{2} \longrightarrow \mathrm{Ca}_{3} \mathrm{N}_{2}\).(b) Potassium and Bromine react to form Potassium bromide. Thus, the completed equation is \(\mathrm{K} + \mathrm{Br}_{2} \longrightarrow \mathrm{KBr}\).(c) Aluminum reacts with Oxygen to form Aluminum Oxide. The completed formula is \(\mathrm{Al} + \mathrm{O}_{2} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}\).

Balance the Chemical Equations

The last and vital step is to balance the resulting chemical equations. This is to ensure that the number of atoms for each element is the same on both sides of the equation. (a) The balanced equation for \(\mathrm{Ca} + \mathrm{N}_{2} \longrightarrow \mathrm{Ca}_{3} \mathrm{N}_{2}\) is \(\mathrm{3Ca} + \mathrm{N}_{2} \longrightarrow \mathrm{Ca}_{3} \mathrm{N}_{2}\).(b) The balanced equation of \(\mathrm{K} + \mathrm{Br}_{2} \longrightarrow \mathrm{KBr}\) is \(\mathrm{2K} + \mathrm{Br}_{2} \longrightarrow \mathrm{2KBr}\).(c) The balanced equation for \(\mathrm{Al} + \mathrm{O}_{2} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}\) is \(\mathrm{4Al} + \mathrm{3O}_{2} \longrightarrow \mathrm{2Al}_{2} \mathrm{O}_{3}\).

Key concepts

Combination Reactions

Imagine you are baking a cake. You mix different ingredients to create something new and delicious. Similarly, in chemistry, a combination reaction is a type of chemical process where two or more substances combine to form a single product. This kind of reaction can involve elements or compounds that react together to create a complex compound.

Using our textbook exercise as an example, when calcium (Ca) reacts with nitrogen gas (N2), they form calcium nitride (Ca3N2). Other examples include potassium (K) combining with bromine (Br2) to produce potassium bromide (KBr), and aluminum (Al) reacting with oxygen gas (O2) to form aluminum oxide (Al2O3).

These reactions are important in the formation of many compounds and are fundamental to understanding how elements come together to form new substances.

Chemical Equation

In chemistry, a chemical equation is a symbolic representation of a chemical reaction. It shows the reactants (the starting substances) on the left side and the products (the resulting substances) on the right side, separated by an arrow indicating the direction of the reaction. Each chemical substance is represented by its chemical formula and appropriate coefficients are used to balance the equation.

For instance, the chemical equation \( \mathrm{2K} + \mathrm{Br}_{2} \longrightarrow \mathrm{2KBr} \) represents how potassium and bromine react to form potassium bromide. Learning to write and balance chemical equations is a key skill in chemistry that allows us to predict the outcomes of reactions and understand the changes occurring on a molecular level.

Reactants and Products

The substances that undergo change in a chemical reaction are known as reactants, and the new substances formed are called products. In the context of our exercise, calcium (\r\(\mathrm{Ca}\)), potassium (\r\(\mathrm{K}\)), and aluminum (\r\(\mathrm{Al}\)) are reactants that undergo combination reactions with nitrogen gas (\r\(\mathrm{N}_{2}\)), bromine (\r\(\mathrm{Br}_{2}\)), and oxygen gas (\r\(\mathrm{O}_{2}\)), respectively.

The transformation of reactants into products is the essence of chemical reactions. By understanding the properties of reactants and products, chemists can manipulate conditions to steer reactions in desirable directions, leading to advancements in fields like medicine, energy, and materials science.

Stoichiometry

The term stoichiometry stems from two Greek words meaning 'element' and 'measure.' It is the part of chemistry that deals with the calculation of quantities of substances involved in chemical reactions. Balancing chemical equations is an integral part of stoichiometry as it ensures the law of conservation of mass is respected; meaning, the mass of the reactants must be equal to the mass of the products.

In our textbook solutions, balancing the equation involves adding coefficients to ensure that there are an equal number of atoms for each element on both sides. For aluminum and oxygen reacting to form aluminum oxide, we balance the equation to reflect that four aluminum atoms react with three oxygen molecules to produce two molecules of aluminum oxide (\(\mathrm{4Al} + \mathrm{3O}_{2} \longrightarrow \mathrm{2Al}_{2} \mathrm{O}_{3}\)). Achieving stoichiometric balance is crucial for accurately predicting the amounts of reactants needed and products formed in a chemical reaction.