Problem 40 - Chemistry: Principles and Reactions

Question

Hexachlorophene, a compound made up of atoms of carbon, hydrogen, chlorine, and oxygen, is an ingredient in germicidal soaps. Combustion of a \(1.000-\mathrm{g}\) sample yields \(1.407 \mathrm{~g}\) of carbon dioxide, \(0.134 \mathrm{~g}\) of water, and \(0.523 \mathrm{~g}\) of chlorine gas. What are the mass percents of carbon, hydrogen, oxygen, and chlorine in hexachlorophene?

Step-by-Step Solution

Answer

Answer: The mass percents of carbon, hydrogen, oxygen, and chlorine in hexachlorophene are approximately 38.396%, 1.4999%, 7.8041%, and 52.3%, respectively.

Step 1: Calculate the moles of CO₂, H₂O, and Cl₂ produced

To get started, we will use the masses of CO₂, H₂O, and Cl₂ produced to find the moles of each substance. We will use the molar mass of each compound to do this, which are: - CO₂: 12.01 g/mol (C) + 2 * 16.00 g/mol (O) = 44.01 g/mol - H₂O: 2 * 1.008 g/mol (H) + 16.00 g/mol (O) = 18.02 g/mol - Cl₂: 2 * 35.45 g/mol (Cl) = 70.90 g/mol Now, let's convert the masses to moles: - Moles of CO₂: (1.407 g) / (44.01 g/mol) = 0.03198 mol - Moles of H₂O: (0.134 g) / (18.02 g/mol) = 0.007442 mol - Moles of Cl₂: (0.523 g) / (70.90 g/mol) = 0.007372 mol

Step 2: Convert moles to grams for each element

Next, we need to convert the moles of each substance to grams of individual elements: - Grams of C: (0.03198 mol) * (12.01 g/mol) = 0.38396 g - Grams of H: (0.007442 mol) * (2 * 1.008 g/mol) = 0.01499904 g - Grams of Cl: (0.007372 mol) * (2 * 35.45 g/mol) = 0.523 g Since we are given a 1.000 g sample and we've found the amount of three elements, we can find the amount of the remaining element, oxygen (O), by subtraction: - Grams of O: 1.000 g - (0.38396 g + 0.01499904 g + 0.523 g) = 0.07804096 g

Step 3: Calculate the mass percents of each element

Finally, we can calculate the mass percent of each element in hexachlorophene by dividing the mass of each element by the total mass of the sample (1.000 g) and multiplying by 100. - Mass percent of C: (0.38396 g / 1.000 g) * 100 = 38.396% - Mass percent of H: (0.01499904 g / 1.000 g) * 100 = 1.4999% - Mass percent of Cl: (0.523 g / 1.000 g) * 100 = 52.3% - Mass percent of O: (0.07804096 g / 1.000 g) * 100 = 7.8041% Thus, the mass percents of carbon, hydrogen, oxygen, and chlorine in hexachlorophene are approximately 38.396%, 1.4999%, 7.8041%, and 52.3%, respectively.

Key Concepts

Understanding Hexachlorophene

Hexachlorophene is a chemical compound utilized predominantly for its antimicrobial properties. It's often found in germicidal soaps and other hygiene products. This compound consists of four key elements: carbon, hydrogen, chlorine, and oxygen. These elements combine in specific proportions to form the molecular structure of hexachlorophene, which contributes to its effectiveness against bacteria.
The distinct feature of hexachlorophene is its inclusion of chlorine atoms. Chlorine gives it its germicidal capabilities, making it effective in reducing and controlling bacterial concentrations on the skin.

• Hexachlorophene in combination with other compounds helps maintain hygiene.
• The presence of chlorine helps in killing bacteria and other pathogens.
• As a solid, it requires careful handling due to its potential hazards when misused.

Despite its benefits, commercial usage of hexachlorophene in over-the-counter products is restricted in several regions due to potential health risks such as skin irritation.

Exploring Combustion Analysis

Combustion analysis is a critical technique used in chemistry to determine the elemental composition of unknown substances. In the context of hexachlorophene, combustion analysis helps identify the percentages of carbon, hydrogen, oxygen, and chlorine within the compound.
The process involves burning a sample to produce specific combustion products, usually carbon dioxide (CO₂), water (H₂O), and sometimes chlorine gas (Cl₂). Measuring the masses of these products allows chemists to calculate the original masses of the elements in the sample.

• This method provides a practical way to verify the empirical formula of a compound.
• By analyzing the combustion products, you can deduce the amounts of each element present.
• It requires careful measurement and calculation to ensure accuracy.

In the specific case of hexachlorophene, knowing how much of each gas is produced helps in calculating the mass percent composition, providing valuable information about its molecular structure.

The Role of Stoichiometry

Stoichiometry plays a crucial role in understanding chemical reactions and compositions. In the exercise involving hexachlorophene, stoichiometry helps calculate how elements are distributed within the compound.
This involves using the balanced equations for combustion. Starting with the masses of the combustion products, stoichiometry allows for the conversion of these masses into moles using molar masses. These mole calculations help determine the amounts of carbon, hydrogen, and chlorine initially present in hexachlorophene.

• Stoichiometry is used to understand the proportions of elements undergoing reactions.
• It facilitates conversion between mass and moles, essential for finding mass percentages.
• Accurate stoichiometric calculations ensure precise understanding of molecular composition.

In summary, stoichiometry is indispensable for analyzing chemical compositions, as it underlines the quantitative relationships necessary for understanding complex compounds like hexachlorophene.