Write a balanced chemical equation for each reaction. a. Solid copper reacts with solid sulfur to form solid copper(I) sulfide. b. Solid iron(III) oxide reacts with hydrogen gas to form solid iron and liquid water. c. Sulfur dioxide gas reacts with oxygen gas to form sulfur trioxide gas. d. Gaseous ammonia (NH \(_{3} )\) reacts with gaseous oxygen to form gaseous nitrogen monoxide and gaseous water.

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Thus, the number of atoms for each element must be the same on both sides of a chemical equation.

When balancing chemical equations, like those given in the exercise, stoichiometry lets us calculate the exact amount of reactants needed to react together to form specific products. It also allows us to predict the amounts of products formed from given quantities of reactants. In the provided solutions, stoichiometry principles are applied meticulously to ensure that all atoms are accounted for and the equations are balanced.

One critical aspect of stoichiometry is using coefficients, which are numbers placed before compounds in a chemical equation to show the ratio in which substances react or are produced. These coefficients reflect the mole ratio of the reactants and products, tying directly into the mole concept.

A chemical reaction is a process in which substances, the reactants, undergo chemical transformation to become different substances, called products. The reactants and products in a chemical reaction are connected by a chemical equation, which shows how atoms and molecules are rearranged.

In the textbook exercise, different types of reactions are presented, such as the formation of copper(I) sulfide from copper and sulfur, and the combustion of ammonia to form nitrogen monoxide and water. During these reactions, chemical bonds are broken and formed, resulting in new substances with different properties from the original reactants. Balancing chemical equations is crucial in representing these reactions accurately. It ensures that the same number of each type of atom appears on both sides of the equation, reflecting the conservation of mass principle.

The mole concept is a fundamental principle of chemistry that provides a way to measure the amount of a substance. A mole is defined as the amount of a substance that contains as many entities (atoms, molecules, ions, or other particles) as there are atoms in 12 grams of carbon-12. This number is known as Avogadro’s number, approximately equal to 6.022 × 10²³.

The mole concept allows chemists to count and use specific quantities of atoms and molecules in calculations and chemical reactions. In the context of balancing chemical reactions, one mole of any substance must balance one mole of another according to the coefficients determined in the balanced equation. For example, in the ammonia and oxygen reaction from the exercise, a mole ratio of 4:5 is needed when combining ammonia and oxygen to produce nitrogen monoxide and water according to the balanced equation.