Lab #1 VB#1: Determination of the Empirical Formula of Silver Oxide

Introduction

• Chemical Compounds: Over 20 million organic and inorganic compounds are recognized in the chemical abstracts database.
• Identification: Compounds are identified by their composition.

Background

• Composition Description Methods:
  1. Percent Composition:
     • Gives percent by mass of each element in a compound.
     • Elements in a compound are always in the same mass proportion (Law of Definite Proportions).
  2. Empirical Formula:
     • Simplest whole-number ratio of atoms.
     • Experimentally determined.
     • May not represent actual atom numbers; different compounds can share the same empirical formula.
  3. Molecular Formula:
     • Indicates the actual number of atoms in a molecule.
     • Unique for each compound; simple multiple of the empirical formula.
     • Requires molar mass for determination.

Experiment Overview

• Objective: Determine percent composition and empirical formula of silver oxide.
• Process:
  • Silver oxide decomposes into silver metal and oxygen when heated.
  • Mass of silver oxide = Mass of silver metal + Mass of oxygen.
  • Measure initial mass of silver oxide and final mass of silver metal to determine oxygen mass loss.

Pre-lab Questions

1. Convert mass of iron to moles using its molar mass.
2. Determine mass of oxygen reacted using conservation of mass.
3. Calculate moles of oxygen in iron oxide.
4. Determine empirical formula of iron oxide by moles ratio.

Lab Procedure & Data Table

• Data Collected: Mass of crucible, lid, silver oxide, and silver metal for multiple trials.

Post-Lab Calculations

1. Calculate mass of silver oxide and silver metal; use conservation law for oxygen.
2. Determine percent composition of silver and oxygen in silver oxide.
3. Calculate moles of each element using molar masses.
4. Find mole ratio Ag/O and empirical formula for silver oxide.
5. Write balanced equation for silver oxide decomposition.
6. Calculate theoretical yield of silver metal.
7. Compute percent yield using formula.
8. Discuss experimental error sources.

Key Concepts

• Law of Conservation of Mass: Total mass of products equals reactants.
• Empirical Formulas: Calculated from experimental data.
• Percent Yield: Relates actual versus theoretical maximum product formed.
• Error Analysis: Identifies reasons for deviation in expected results.

These notes cover the essential aspects of determining the empirical formula of silver oxide, highlighting the process to find percent compositions, perform calculations, and analyze results.