Problem 59 - Chemistry The Science in Context

Question

Does the sum of the masses of the products always equal the sum of the masses of the reactants in a balanced chemical equation?

Step-by-Step Solution

Answer

Question: Explain the concept of conservation of mass in a balanced chemical equation and how it shows that the sum of the masses of the products always equals the sum of the masses of the reactants. Answer: The concept of conservation of mass in a balanced chemical equation is based on the Law of Conservation of Mass, which states that mass cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants before the reaction must be equal to the total mass of the products after the reaction. In a balanced chemical equation, the number of atoms for each element is conserved by adjusting the coefficients. With this balance, the masses of the reactants and products can be calculated using their molar masses. When the sum of the masses of the reactants is compared to the sum of the masses of the products, they must be equal, as dictated by the Law of Conservation of Mass.

Step 1: Understand the Law of Conservation of Mass

The Law of Conservation of Mass states that mass cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants before the reaction must be equal to the total mass of the products after the reaction. Therefore, the sum of the masses of the products always equals the sum of the masses of the reactants in a balanced chemical equation.

Step 2: Determine the Reactants and Products

In order to verify that the sum of the masses of the products always equals the sum of the masses of the reactants, we need to identify the reactants and products in a balanced chemical equation. The reactants are the substances present before the reaction and are usually written on the left side of the equation, while the products are the substances that are formed during the reaction and are usually written on the right side of the equation.

Step 3: Balance the Chemical Equation

The next step is to balance the chemical equation. A balanced chemical equation has the same number of atoms of each element on both sides of the equation. Balancing a chemical equation involves adjusting the coefficients (the numbers in front of the chemical formulas) such that the number of atoms for each element is conserved.

Step 4: Calculate the Masses of the Reactants and Products

Using the balanced chemical equation and the coefficients, the masses of the reactants and products can be calculated using the molar masses for each molecule. The molar mass is the sum of the atomic masses of all the atoms in the molecule, and it is usually given in grams per mole (g/mol). The mass of a reactant or product can then be calculated as: (number of moles) * (molar mass).

Step 5: Compare the Masses of the Reactants and Products

After calculating the masses of the reactants and products, compare the sum of the masses of the reactants to the sum of the masses of the products. Since the law of conservation of mass states that mass cannot be created or destroyed, the sum of the masses of the reactants must equal the sum of the masses of the products in a balanced chemical equation.

Step 6: Conclusion

In conclusion, the sum of the masses of the products always equals the sum of the masses of the reactants in a balanced chemical equation, as dictated by the Law of Conservation of Mass. By understanding this fundamental concept in chemistry, we can better understand how chemical reactions occur without violating this essential law in nature.

Key Concepts

Balanced Chemical Equation

In chemistry, a balanced chemical equation is an expression that represents a chemical reaction, showing the relationship between the reactants and the products. It is crucial for the equation to be balanced because it ensures that the Law of Conservation of Mass is honored.

The balancing process involves using coefficients to adjust the number of molecules or atoms on each side of the equation. This way, the numbers of atoms for each element are equal for both the reactants and products. The primary goal is to make sure that no atom is lost or gained in a reaction, which aligns with the notion that matter cannot be created or destroyed.

• In a balanced equation:
  \( \text{aX} + \text{bY} \rightarrow \text{cZ} \)
• The coefficients \( a, b, \) and \( c \) are chosen so that the number of each type of atom is the same on both sides.
• This balance is necessary for accurate experimental outcomes and calculations, especially when determining other properties such as mass or reactions yields.

Reactants and Products

In any chemical reaction, you will encounter two primary types of substances: reactants and products. Reactants are the substances that initially undergo the chemical transformation. They are typically found on the left side of a chemical equation.

Products, on the other hand, are the substances that are formed as a result of the reaction. These are placed on the right side of the chemical equation.

• Reactants:
  - Are the starting materials.
  - Undergo change during the reaction.
• Products:
  - Are new substances created.
  - Result from the rearrangement of atoms.

During a chemical reaction, bonds between atoms in the reactants are broken, and new bonds are formed to create the products. Identifying these entities is essential, not just for documentation in an equilibrium equation, but also for experimental design and chemical analysis.

Molar Mass

Molar mass is a crucial concept when dealing with chemical equations as it allows one to calculate the mass of a substance in terms of moles. Molar mass, usually expressed in grams per mole (g/mol), represents the mass of one mole of a given substance, be it an element or compound.

Calculating the molar mass involves summing up the atomic masses of all atoms present in a molecule as indicated in the periodic table. This is essential when converting between the mass of a substance and the number of moles, facilitating the practical comparison of reactants and products.

• For example, in water (\(H_2O\)):
  - Molar mass of hydrogen is approximately 1 g/mol.
  - Molar mass of oxygen is approximately 16 g/mol.
  - Thus, the molar mass of water is: \( (2 \times 1) + 16 = 18 \text{ g/mol} \).

This understanding is fundamental in calculations related to chemical reactions, as it helps to verify whether the total mass remains constant, in adherence to the Law of Conservation of Mass.