Reaction Stoichiometry for Iron (II) or (III) Determination
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Student Procedure
Teacher Annotated Procedure
Sample Data, Calculation & Analysis
GoogleSheet Data & Analysis
SUMMARY/ OVERVIEW:
Students determine the reaction equation between metallic iron and copper(II) sulfate by stoichiometry. By reacting a known mass of iron with excess $\text{CuSO}_4$ and weighing the copper metal produced, students calculate the mole ratio to deduce whether $\text{Fe}^{2+}$ or $\text{Fe}^{3+}$ is formed.
ESTIMATE TIME ⏰: 90 minutes
The lab requires careful measurement and often involves a drying step, necessitating two lab periods
Reaction and Initial Measurements (45 minutes)
Final Measurements (15 minutes)
SAFETY PRECAUTIONS:
Eye Protection is Mandatory: Always wear approved safety goggles throughout the entire experiment.
Handle Copper(II) Sulfate with Care: Copper(II) sulfate is toxic by ingestion and can be irritating.
Prevent Ingestion: Wash hands thoroughly with soap and water before leaving the lab.
Proper Waste Disposal: Dispose of all chemical waste, especially the excess copper(II) sulfate solution and the filtrate (the aqueous iron sulfate product), in the designated waste containers as instructed by your teacher. Do not pour them down the sink.
Introduction
The Stoichiometry of Iron-Copper Reaction lab explores a fundamental concept in chemistry: stoichiometry, which governs the quantitative relationships between reactants and products in a balanced chemical reaction. This experiment centers on a single displacement redox reaction between solid metallic iron ($\text{Fe}$) and an aqueous solution of copper(II) sulfate ($\text{CuSO}_4$).
Core Concepts
Redox Reaction: The reaction involves the transfer of electrons. Metallic iron is oxidized (loses electrons), and copper(II) ions ($\text{Cu}^{2+}$) are reduced (gain electrons).
Stoichiometric Ratio: The primary goal is to determine the unknown mole ratio between the iron used and the copper produced. This ratio reveals which iron ion, $\text{Fe}^{2+}$ or $\text{Fe}^{3+}$, is formed during the reaction.
Law of Conservation of Mass: By carefully measuring the masses of the metals before and after the reaction, students confirm that matter is conserved, even as it changes form.
Background
The reaction involves the more reactive iron displacing the less reactive copper from the solution.1 The specific products formed lead to two possible balanced equations:
Case 1: Iron(II) Product ($\text{Fe}^{2+}$ is formed)
$$\text{Fe}(\text{s}) + \text{CuSO}_4(\text{aq}) \rightarrow \text{Cu}(\text{s}) + \text{FeSO}_4(\text{aq})$$
Mole Ratio ($\text{Fe}:\text{Cu}$): $\mathbf{1:1}$
Case 2: Iron(III) Product ($\text{Fe}^{3+}$ is formed)
$$2\text{Fe}(\text{s}) + 3\text{CuSO}_4(\text{aq}) \rightarrow 3\text{Cu}(\text{s}) + \text{Fe}_2(\text{SO}_4)_3(\text{aq})$$
Mole Ratio ($\text{Fe}:\text{Cu}$): $\mathbf{2:3}$
The experimental goal is to gather mass data that allows calculation of the $\text{Fe}:\text{Cu}$ mole ratio and conclusively distinguish between these two possibilities.