Problem 78 - Chemistry: An Atoms-Focused Approach

Question

Which substance in each of the following pairs of quantities contains more moles of oxygen? a. \(2 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}\) or \(1 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}_{5}\) b. \(1 \mathrm{mol} \mathrm{NO}\) or \(1 \mathrm{mol} \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}\) c. \(2 \mathrm{mol} \mathrm{NO}_{2}\) or \(1 \mathrm{mol} \mathrm{NaNO}_{2}\)

Step-by-Step Solution

Answer

a. 2 mol N2O or 1 mol N2O5 b. 1 mol NO or 1 mol Ca(NO3)2 c. 2 mol NO2 or 1 mol NaNO2 Answer: a. N2O5 contains more moles of oxygen. b. Ca(NO3)2 contains more moles of oxygen. c. 2 mol NO2 contains more moles of oxygen.

Step 1: Calculate moles of Oxygen in 2 mol N2O

We have 2 moles of N2O, and each molecule contains 1 oxygen atom. Therefore, there are 2 moles of O in 2 mol N2O.

Step 2: Calculate moles of Oxygen in 1 mol N2O5

We have 1 mole of N2O5, and each molecule contains 5 oxygen atoms. Therefore, there are 5 moles of O in 1 mol N2O5. #a. Answer:#: N2O5 contains more moles of oxygen. #b. 1 mol NO or 1 mol Ca(NO3)2#

Step 3: Calculate moles of Oxygen in 1 mol NO

We have 1 mole of NO, and each molecule contains 1 oxygen atom. Therefore, there is 1 mole of O in 1 mol NO.

Step 4: Calculate moles of Oxygen in 1 mol Ca(NO3)2

We have 1 mole of Ca(NO3)2, and each molecule contains 2 moles of NO3, and each NO3 contains 3 oxygen atoms. Therefore, there are 6 moles of O in 1 mol Ca(NO3)2. #b. Answer#: Ca(NO3)2 contains more moles of oxygen. #c. 2 mol NO2 or 1 mol NaNO2#

Step 5: Calculate moles of Oxygen in 2 mol NO2

We have 2 moles of NO2, and each molecule contains 2 oxygen atoms. Therefore, there are 4 moles of O in 2 mol NO2.

Step 6: Calculate moles of Oxygen in 1 mol NaNO2

We have 1 mole of NaNO2, and each molecule contains 1 mole of NO2, and each NO2 contains 2 oxygen atoms. Therefore, there are 2 moles of O in 1 mol NaNO2. #c. Answer#: 2 mol NO2 contains more moles of oxygen.

Key Concepts

Chemical Formulas

Chemical formulas are a way of expressing information about the atoms that make up a particular chemical compound. Each chemical formula consists of element symbols and numerical subscripts, indicating the number of atoms of each element present.
For example, the compound \( \text{N}_2\text{O}_5 \) has a chemical formula that tells us there are two nitrogen atoms and five oxygen atoms per molecule. This basic structure is essential for studying and understanding chemical reactions and molecular interactions.

• Element Symbols: Represent the elements in a compound, e.g., H for Hydrogen, O for Oxygen.
• Numerical Subscripts: Indicate the amount of each type of atom in the molecule.
• Aggregation: When elements combine in different ratios, they form different compounds.

Chemical formulas not only identify what a substance is, but they also hint at its potential chemical behavior and how it might interact with other compounds.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the amounts of reactants and products in a chemical reaction.
This essential concept helps chemists determine how much of a substance is required or produced in a given reaction. When calculating stoichiometric relationships, it is crucial to understand the chemical equations that represent these reactions.

• Mole Concept: The heart of stoichiometric calculations, moles allow chemists to count atoms by weighing them.
• Balanced Equations: Chemical equations must be balanced to maintain equal numbers of atoms for each element on both sides of the equation.
• Conversion Factors: These help convert between grams, moles, and molecules to perform stoichiometric calculations effectively.

Understanding stoichiometry is vital for making predictions about the outcomes of chemical reactions, such as determining the amount of moles of oxygen in a given compound.

Molecular Composition

Molecular composition refers to the types and amounts of atoms that make up a molecule or compound. Knowing the molecular composition of a compound is crucial for understanding its properties and behavior during chemical reactions.
For instance, in the exercise provided, we determined which compounds contained more moles of oxygen, based on the molecular composition:

• \( \text{N}_2\text{O} \) consists of one nitrogen molecule and one oxygen molecule, leading us to 2 moles of O in 2 moles of \( \text{N}_2\text{O} \).
• \( \text{Ca(NO}_3)_2 \) is composed of one calcium atom and two nitrate groups, each containing three oxygen atoms, resulting in 6 moles of oxygen per mole of \( \text{Ca(NO}_3)_2 \).
• \( \text{NO}_2 \) contains one nitrogen atom and two oxygen atoms in each molecule, leading to 4 moles of O in 2 moles of \( \text{NO}_2 \).

Understanding molecular composition can help predict how a substance might react or what products might be formed during a chemical reaction, assisting in fields from material science to pharmacology.