Problem 51 - Chemistry Matter and Change

Question

A 13.0 -g sample of X combines with a \(34.0-\mathrm{g}\) sample of \(\mathrm{Y}\) to form the compound \(\mathrm{XY}_{2} .\) What is the mass of the reactants?

Step-by-Step Solution

Answer

The mass of the reactants is 47.0 g.

Step 1: Understanding the Problem

To solve this exercise, begin by identifying the key information provided. We have a 13.0-g sample of Substance X and a 34.0-g sample of Substance Y that react together. We need to determine the total mass of the reactants, which refers to the combined mass of these two substances before they form the compound XY₂.

Step 2: Identify the Reactants

The reactants are the substances that are present before the chemical reaction occurs. In this case, Substance X and Substance Y are the reactants. The masses of these reactants are given as 13.0 g for X and 34.0 g for Y.

Step 3: Calculate the Total Mass of the Reactants

We find the mass of the reactants by adding the mass of Substance X to the mass of Substance Y. This is calculated as follows: 13.0 g (mass of X) + 34.0 g (mass of Y).

Step 4: Perform the Addition

Now, perform the addition: \[ 13.0 ext{ g} + 34.0 ext{ g} = 47.0 ext{ g} \] Thus, the total mass of the reactants is 47.0 g.

Key Concepts

Understanding Chemical Reactions

Chemical reactions are processes where substances known as reactants are transformed into different substances called products. This transformation involves the rearrangement of atoms. During a chemical reaction:

• The identity of the reactants is changed, and they form new bonds.
• Energy can either be absorbed or released, depending on the specific reaction.
• Substances before the reaction (reactants) and after the reaction (products) are involved in a strict conservation of mass, meaning the total mass remains constant.

For example, in the reaction described by the exercise, substances X and Y react to form the compound XY₂. This signifies a chemical reaction has occurred because the original reactants are transformed and new chemical bonds are formed, resulting in a compound with different properties.

Role of Reactants in Chemical Reactions

Reactants are the starting materials in a chemical reaction. Understanding the role of reactants is crucial to predicting the outcomes of a reaction:

• In any given reaction, reactants come together and undergo changes to form products.
• Each reactant has a specific mass or amount that must be known to predict how much product will be formed.
• The reaction process often involves breaking old bonds and forming new ones, which reorganizes the atoms.

In this exercise, the reactants are X and Y, with their masses given as 13.0 g and 34.0 g, respectively. These masses are essential for calculating the total mass of reactants and ensuring mass conservation in the reaction.

Mastering Stoichiometry

Stoichiometry is a branch of chemistry that focuses on the quantitative aspects of chemical formulas and reactions. It allows us to calculate the relative quantities of reactants and products in a chemical reaction:

• Stoichiometry uses balanced chemical equations to represent the proportions in which reactants combine and products form.
• These equations help predict how much product can be obtained from a given amount of reactants, or how much reactant is needed to produce a certain amount of product.
• This concept relies heavily on the law of conservation of mass, which ensures that matter is neither created nor destroyed in a chemical reaction.

In the provided exercise, stoichiometry would guide us in determining how the masses of X (13.0 g) and Y (34.0 g) combine to exactly form the mass of the resulting compound XY₂. By adding the masses of X and Y, we ensure that the mass conservation principle is upheld in this stoichiometric relationship.