Problem 105 - Chemistry Matter and Change

Question

Observe and Infer Determine whether each reaction depends on a limiting reactant. Explain why or why not, and identify the limiting reactant. a. Potassium chlorate decomposes to form potassium chloride and oxygen. b. Silver nitrate and hydrochloric acid react to produce silver chloride and nitric acid.

Step-by-Step Solution

Answer

Since the exercise does not provide the amounts of the reactants, it is not possible to determine whether a limiting reactant is present or to identify it in either reaction. To determine the limiting reactant, the amounts of reactants would need to be given and then compared according to their stoichiometric ratios in the balanced chemical equations. If the given amounts of reactants don't match their stoichiometric ratios, the reactant with the lowest ratio would be the limiting reactant.

Step 1: Identify the given reactants and their amounts

To determine the limiting reactant, we must know the amounts of each reactant involved in the reaction. However, this information is not given in the exercise. Depending on the amounts of reactants provided, the reactions may or may not have a limiting reactant.

Step 2: Assess whether the reactions have a limiting reactant

If the amounts of reactants are given, the limiting reactant can be determined using stoichiometry. If the stoichiometric ratios of reactants are equal, there is no limiting reactant in the reaction because the reactants will be consumed simultaneously, and the reaction will go to completion. However, if the stoichiometric ratios of reactants are not equal, one reactant will be consumed before the others, making it the limiting reactant.

Step 3: Identify the limiting reactant

Assuming the information about reactant amounts was given, we could identify the limiting reactant by using the stoichiometric ratios in the balanced chemical equations. If the given amounts of reactants don't match their stoichiometric ratios in the balanced equation, the reactant with the lowest ratio would be the limiting reactant. Considering that the exercise does not provide the amounts of the reactants, it is not possible to determine whether a limiting reactant is present or to identify it. We can only explain the process of determining and identifying the limiting reactant in each reaction, as outlined in the steps above.

Key Concepts

Chemical Reaction

In a chemical reaction, substances known as reactants interact to form new substances called products. This transformation involves breaking original chemical bonds and forming new ones. The process alters the identity and properties of the materials involved.
A chemical reaction is a fundamental concept in chemistry, governing how atoms rearrange to create different compounds. For example, when potassium chlorate ( KClO_3 ) decomposes, it produces potassium chloride ( KCl ) and oxygen ( O_2 ).

• Reactants: The starting materials in a chemical reaction.
• Products: The substances formed as a result of a chemical reaction.
• Chemical Bonds: The attractions holding atoms together in a molecule, which are broken and reformed during reactions.

The main goal of studying chemical reactions is to understand how reactants transform into products and to predict the outcomes and properties of new substances formed. Understanding chemical reactions is vital in industries like pharmaceuticals, agriculture, and energy, where new products with specific attributes are continuously developed.

Stoichiometry

Stoichiometry is a branch of chemistry focused on the quantitative relationships between the reactants and products in a chemical reaction. It is based on the conservation of mass and the principle that atoms are neither created nor destroyed in a chemical reaction.
Stoichiometry allows chemists to predict the amount of products formed in a reaction given the starting amounts of reactants.

• Stoichiometric Ratios: The proportion of reactants compared to products in a chemical equation, determined by the coefficients of the balanced equation.
• Limiting Reactant: The reactant that is completely consumed in a reaction, determining the maximum amount of product that can be formed.
• Excess Reactant: The reactant that remains after the limiting reactant is completely used up.

Using stoichiometry involves mol-to-mol conversions, where the coefficients from the balanced equation provide the conversion factors. This is crucial for effectively managing resources, especially in large-scale chemical manufacturing and processing to ensure efficient use of reactants.

Balanced Chemical Equation

A balanced chemical equation accurately represents a chemical reaction with equal numbers of atoms for each element in the reactants and products. Balancing equations ensures compliance with the Law of Conservation of Mass, which states that matter cannot be created or destroyed.
Let's delve deeper into this concept:

• Coefficients: Numbers placed before compounds in a chemical equation to indicate the number of molecules or moles involved in the reaction.
• Law of Conservation of Mass: This law asserts that the mass of the reactants must equal the mass of the products.
• Equal Atom Count: Ensures that across the equation, every atom in the reactants equals those in the products.

To balance a chemical equation, one adjusts these coefficients so each element has the same number of atoms in both sides of the equation. This technique is essential for correctly applying stoichiometry and determining the limiting reactant in a reaction. Balancing equations is foundational in chemistry and necessary for precise predictions in both academic and applied chemical contexts.