Problem 47 - Chemistry The Science in Context

Question

In a balanced chemical equation, must the sum of the masses of all the gaseous reactants always equal the sum of the masses of the gaseous products?

Step-by-Step Solution

Answer

Answer: Yes, in a balanced chemical equation, the sum of the masses of all gaseous reactants always equals the sum of the masses of all gaseous products. This is because the Law of Conservation of Mass ensures that the mass of reactants equals the mass of products, regardless of their state of matter (solid, liquid, or gas).

Step 1: Understand the Law of Conservation of Mass

The Law of Conservation of Mass states that in a closed system, the mass of the reactants must equal the mass of the products. This law is a fundamental principle guiding all chemical reactions. It implies that matter cannot be created or destroyed, only changed in state or their arrangement.

Step 2: Understand the concept of a balanced chemical equation

A balanced chemical equation represents a chemical reaction where the number of atoms of each element is equal on both sides of the equation (reactants and products). In other words, the total mass of reactants in a balanced equation will be equal to the total mass of products.

Step 3: Apply the balanced chemical equation to gaseous reactants and products

Since a balanced chemical equation ensures that the total mass of reactants is equal to the total mass of products, this principle applies to gaseous reactants and products as well. Therefore, in a balanced chemical equation, the sum of the masses of all gaseous reactants will always equal the sum of the masses of all gaseous products because the law of conservation of mass remains valid regardless of the state of matter (solid, liquid, or gas).

Key Concepts

Law of Conservation of Mass

One of the cornerstone principles in chemistry is the Law of Conservation of Mass. This fundamental concept asserts that mass is neither created nor destroyed in a closed system. In the context of a chemical reaction, this means that all mass present in the reactants must be accounted for in the products. It is an echo of the scientific understanding that matter is persistent; it can transform from one substance to another and change in state (from solid to liquid to gas), but the total mass remains constant.

Consider this as nature's bookkeeping system, ensuring that during a reaction, every atom that enters as a reactant exits within the product, although possibly in a different molecular arrangement. This law lays the groundwork for understanding reactions quantitatively and balancing chemical equations, which is a skill fundamental to chemistry studies.

Chemical Reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemists represent these reactions with chemical equations that illustrate the substances involved. The reactants, or starting materials, are listed on the left side of the equation, while the products, or substances formed, are on the right side.

Every chemical equation must reflect the Law of Conservation of Mass, meaning all atoms present in the reactants must appear in the products. A balanced chemical equation, therefore, is a representation of this law, serving as proof that a reaction adheres to nature's rule of mass persistence. Balancing an equation is like solving a puzzle, ensuring that the same number of each type of atom appears on both sides of the equation, effectively confirming that no mass is gained or lost during the reaction.

Mass of Reactants and Products

In the realm of chemistry, the mass of reactants and products in a chemical equation must always balance out when considering the Law of Conservation of Mass. This implies that when you start with a certain mass of reactants, after the reaction has completed, the total mass of the products should be equal to the mass you started with – no more, no less. This holds true for any state of matter, including gases, solids, and liquids.

For example, when dealing with gaseous reactants and products, even though gases can expand and seem to 'disappear', their mass remains part of the system. If a reaction starts with 20 grams of various reactant gases, by the end of the reaction, the sum of the product gases will also weigh 20 grams. The atoms have simply been rearranged into new molecules, and the mass has been conserved. Understanding this concept is crucial for students, as it reinforces the principle that chemical reactions are rearrangements of atoms rather than processes that result in loss or gain of matter.