Einfache Stöchiometrie: Von Molen zu Gramm Übungen - Avogadro und mehr

Problem Solving Steps

This page provides a detailed solution to the percentage yield problem introduced on the previous page. It demonstrates the step-by-step process for solving complex stoichiometry problems involving percentage yield. The solution includes:

1. Writing and balancing the chemical equation
2. Calculating the theoretical yield of Cr
3. Determining the required amounts of C and Cr2O3

The process emphasizes the importance of working backwards from the actual yield to determine the theoretical yield, and then using stoichiometric ratios to calculate the required reactants.

Highlight: In percentage yield calculations, always start by determining the theoretical yield from the given actual yield and percentage.

Example: For 300g Cr at 90% yield, theoretical yield = 300g / 0.90 = 333.3g Cr

Mole-Mole Calculations

This section introduces cálculos químicos ejemplos for mole-to-mole relationships in chemical reactions. It uses the reaction between oxygen and ammonia to produce nitric oxide as an example. Two problems are presented:

1. Calculating moles of NH3 needed to react with 12 moles of O2
2. Determining moles of O2 and NH3 required to produce 28.5 moles of NO

The solutions emphasize the importance of using balanced equations and starting from the given data to solve for unknown quantities.

Example: To find NH3 needed for 12 moles of O2: 12 mol O2 × (4 mol NH3 / 5 mol O2) = 9.6 moles of NH3

Highlight: Any stoichiometric calculation always starts from given data and asks for the quantity of reactants or products.

Mole-Gram Conversions

This section covers conversions between moles and grams, which are fundamental to cálculos estequiométricos en reacciones químicas. Two example problems are presented:

1. Converting 5 grams of KMnO4 to moles
2. Converting 6.5 moles of Na2SO4 to grams

The process involves calculating the molar mass of the compound and then using it to convert between grams and moles. For KMnO4, the molar mass is calculated as 158.09 g/mol, resulting in 0.031 moles. For Na2SO4, the molar mass is 142.06 g/mol, yielding 923.39 grams.

Example: To convert 5 grams of KMnO4 to moles: 5g × (1 mol KMnO4 / 158.09 g KMnO4) = 0.031 moles of KMnO4

Vocabulary: Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).

Gram-Atom/Molecule Conversions

This page explains how to convert between grams and the number of atoms or molecules, which is crucial for understanding cómo calcular la masa en gramos de un elemento. The process involves first converting grams to moles, then using Avogadro's number to determine the number of particles. Examples include:

1. Calculating atoms in 0.6g of Au
2. Calculating molecules in 7.8g of AuCl
3. Calculating ions in 85g of NaOH

Definition: Avogadro's number is 6.022 × 10^23, representing the number of particles in one mole of any substance.

Highlight: One mole of any atom or molecule always contains the same number of particles: 6.022 × 10^23.