Question

Write a balanced equation for the reaction that occurs in each of the following cases: (a) Chlorine reacts with water. (b) Barium metal is heated in an atmosphere of hydrogen gas. (c) Lithium reacts with sulfur. (d) Fluorine reacts with magnesium metal.

Short answer

a) \(Cl_2 + H_2O \rightarrow HCl + HOCl\) b) \(Ba + H_2 \rightarrow BaH_2\) c) \(2 Li + S \rightarrow Li_2S\) d) \(Mg + F_2 \rightarrow MgF_2\)

Step-by-step solution

a) Chlorine reacts with water.

When chlorine (Cl2) reacts with water (H2O), the products are hydrochloric acid (HCl) and hypochlorous acid (HOCl). The balanced equation for this reaction is: Cl2 + H2O -> HCl + HOCl

b) Barium metal is heated in an atmosphere of hydrogen gas.

In this reaction, barium metal (Ba) reacts with hydrogen gas (H2) to form barium hydride (BaH2). The balanced equation for this reaction is: Ba + H2 -> BaH2

c) Lithium reacts with sulfur.

When lithium (Li) reacts with sulfur (S), the product is lithium sulfide (Li2S). The balanced equation for this reaction is: 2 Li + S -> Li2S

d) Fluorine reacts with magnesium metal.

In this case, fluorine (F2) reacts with magnesium metal (Mg) to form magnesium fluoride (MgF2). The balanced equation for this reaction is: Mg + F2 -> MgF2

Key concepts

Chemical Reaction

Understanding a chemical reaction is fundamental when studying chemistry. A chemical reaction is a process where reactants undergo a transformation to become new substances, known as products.

During a reaction, bonds between atoms in the reactants are broken, and new bonds are formed to make the products. This can result in various changes observable to us, such as energy release in the form of light or heat, color change, gas production, or the formation of a precipitate.

For instance, when chlorine reacts with water, this reaction results in the formation of hydrochloric acid and hypochlorous acid, observable through the evolution of gases and a potential temperature change. Each reaction is unique and can range from simple exchange to complex molecular reorganizations.

Chemical Equation

A chemical equation is a symbolic representation of a chemical reaction where the reactants are on the left side and the products on the right, separated by an arrow indicating the direction of the reaction. It includes the chemical symbols and formulas of substances involved.

The art of balancing chemical equations involves making sure that the same number of each type of atom is present on both sides of the equation. This aligns with the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction.

For example, in the reaction of magnesium with fluorine, the balanced chemical equation is written as \( Mg + F_2 \rightarrow MgF_2 \) which shows one magnesium atom reacting with one fluorine molecule to produce one formula unit of magnesium fluoride, keeping the mass balance intact.

Stoichiometry

Stoichiometry is a branch of chemistry that deals with the quantitative relationships, or ratios, between reactants and products in a chemical reaction. It's the tool for figuring out how much of one substance will react with a certain amount of another substance.

In stoichiometry, the coefficients in a balanced chemical equation tell us the relative amounts of reactants and products. With these, we can calculate the mass, volume, and number of particles of any substance involved in a reaction.

Using the barium and hydrogen gas example, \( Ba + H_2 \rightarrow BaH_2 \) shows that one atom of barium reacts with one molecule of hydrogen gas to yield one formula unit of barium hydride. Using stoichiometry, we could determine how much barium is needed to completely react with a certain amount of hydrogen gas.

Reaction of Elements

Elements undergo chemical reactions to achieve a more stable electronic configuration, typically by gaining, losing, or sharing electrons. The ways in which elements react are influenced by their placement on the periodic table and their electron configurations.

Metals such as lithium and magnesium tend to lose electrons to form positive ions or bond with nonmetals, which usually gain electrons to form negative ions. Nonmetals like chlorine and fluorine typically seek to gain electrons during chemical reactions.

When lithium reacts with sulfur, \( 2 Li + S \rightarrow Li_2S \) occurs with lithium donating electrons to sulfur. Understanding how elements react is crucial for predicting the outcomes of chemical reactions and for the synthesis of new materials.