Question

Calculate the mass percent composition of each element in each compound. (a) C2H4O2 (b) CH2O2 (c) C3H9N (d) C4H12N2

Short answer

To find the percent composition of each element, the molar masses of the compounds are determined and used to calculate the mass percent of Carbon, Hydrogen, Oxygen, and Nitrogen in C2H4O2, CH2O2, C3H9N, and C4H12N2 respectively.

Step-by-step solution

Calculate the Molar Mass of Compound (a) C2H4O2

First, determine the molar mass of each element in the compound C2H4O2 by using the periodic table. For this compound: Carbon (C) has a molar mass of 12.01 g/mol, Hydrogen (H) has a molar mass of 1.008 g/mol, Oxygen (O) has a molar mass of 16.00 g/mol. The molar mass of C2H4O2 is calculated as: 2(12.01 g/mol) + 4(1.008 g/mol) + 2(16.00 g/mol).

Calculate the Percent Composition of Each Element in C2H4O2

For C: \( \frac{2 \times 12.01}{Molar\ Mass\ of\ C2H4O2} \times 100 \% \). For H: \( \frac{4 \times 1.008}{Molar\ Mass\ of\ C2H4O2} \times 100 \% \). For O: \( \frac{2 \times 16.00}{Molar\ Mass\ of\ C2H4O2} \times 100 \% \).

Calculate the Molar Mass of Compound (b) CH2O2

For compound CH2O2: Carbon (C) is 12.01 g/mol, Hydrogen (H) is 1.008 g/mol, and Oxygen (O) is 16.00 g/mol. The molar mass of CH2O2 is calculated by: 12.01 g/mol + 2(1.008 g/mol) + 2(16.00 g/mol).

Calculate the Percent Composition of Each Element in CH2O2

For C: \( \frac{12.01}{Molar\ Mass\ of\ CH2O2} \times 100 \% \). For H: \( \frac{2 \times 1.008}{Molar\ Mass\ of\ CH2O2} \times 100 \% \). For O: \( \frac{2 \times 16.00}{Molar\ Mass\ of\ CH2O2} \times 100 \% \).

Calculate the Molar Mass of Compound (c) C3H9N

For compound C3H9N: Carbon (C) is 12.01 g/mol, Hydrogen (H) is 1.008 g/mol, and Nitrogen (N) is 14.01 g/mol. The molar mass of C3H9N is: 3(12.01 g/mol) + 9(1.008 g/mol) + 14.01 g/mol.

Calculate the Percent Composition of Each Element in C3H9N

For C: \( \frac{3 \times 12.01}{Molar\ Mass\ of\ C3H9N} \times 100 \% \). For H: \( \frac{9 \times 1.008}{Molar\ Mass\ of\ C3H9N} \times 100 \% \). For N: \( \frac{14.01}{Molar\ Mass\ of\ C3H9N} \times 100 \% \).

Calculate the Molar Mass of Compound (d) C4H12N2

For compound C4H12N2: Carbon (C) is 12.01 g/mol, Hydrogen (H) is 1.008 g/mol, and Nitrogen (N) is 14.01 g/mol. The molar mass of C4H12N2 is: 4(12.01 g/mol) + 12(1.008 g/mol) + 2(14.01 g/mol).

Calculate the Percent Composition of Each Element in C4H12N2

For C: \( \frac{4 \times 12.01}{Molar\ Mass\ of\ C4H12N2} \times 100 \% \). For H: \( \frac{12 \times 1.008}{Molar\ Mass\ of\ C4H12N2} \times 100 \% \). For N: \( \frac{2 \times 14.01}{Molar\ Mass\ of\ C4H12N2} \times 100 \% \).

Key concepts

Molar Mass Calculation

Understanding the molar mass of a compound is essential in chemistry as it forms the bridge between the mass of a substance and the number of particles or moles present. To calculate the molar mass, you must know the atomic mass of each element in the compound, which is available on the periodic table, and the amount of each element in the formula units.

For example, to find the molar mass of a compound like C2H4O2, you add together the atomic masses of Carbon (C) times two, Hydrogen (H) times four, and Oxygen (O) times two. This yields the formula: \[ Molar\ Mass\ of\ C2H4O2 = 2 \times 12.01\ g/mol + 4 \times 1.008\ g/mol + 2 \times 16.00\ g/mol \] It's the sum of these calculations that gives us the total molar mass of the compound. This step is crucial for further stoichiometric calculations, such as finding the percent composition by mass.

Chemical Formula

A chemical formula represents the types and numbers of atoms in a molecule. It offers a concise way for scientists to communicate complex information. The formula can be empirical, indicating the simplest whole-number ratio of atoms in the compound, or molecular, showing the exact number of atoms of each element in a molecule.

Take the compound C2H4O2 as an example. The subscript numbers indicate there are twice as many carbon and oxygen atoms as there are hydrogen atoms in one molecule of the substance. Understanding the chemical formula is necessary before you can calculate the molar mass or perform stoichiometry.

Stoichiometry

Stoichiometry refers to the quantitative relationships between the amounts of reactants and products in a chemical reaction. It's based on the conservation of mass and the concept of moles. In stoichiometry, the balanced chemical equation serves as a recipe for how much reactant you need to form a certain amount of product.

Using the percent composition by mass, as you have calculated for compounds like C2H4O2, gives you a deeper understanding of these relationships. For example, by knowing the percent by mass of each element, you can determine how much of that element is needed or produced when working with different amounts of reactants and products.

Molecular Composition

Molecular composition involves not only the types and amounts of atoms in a molecular formula but also how these elements are arranged spatially. While the molecular formula gives you the ratio of components, the molecular composition gives you the qualitative and quantitative data about their arrangement and, by extension, their chemical behavior.

Understanding molecular composition is imperative when predicting the properties of compounds and their interactions with other substances. If you grasp this concept, you can interpret how the percent composition by mass, for instance, relates to the molecule's structure and reactivity.