Experiment 3a: Aluminum Content Via Redox Reaction Objective

Experiment 3a Aluminum Content Via Redoxreactionobjectiveto Determin

To determine the aluminum content in commercial samples through stoichiometry and a standard curve of the volume of hydrogen gas produced versus the mass of aluminum consumed.

Paper For Above instruction

Understanding the chemical composition of aluminum in various commercial products is essential in quality control and material verification. The experiment aims to quantify the aluminum content in pure aluminum samples and commercial aluminum foils, specifically Reynolds Wrap and Great Value, through a redox reaction, leveraging stoichiometry and gas volume measurements.

Introduction to Stoichiometry and Reaction Balancing

Stoichiometry involves calculating the ratios of reactants and products in chemical reactions based on their balanced equations. A reaction must be balanced to determine the molar relationships, enabling the calculation of unknown quantities such as the amount of aluminum in a sample. For instance, considering the redox reaction between aluminum and hydrochloric acid:

2Al + 6HCl → 2AlCl₃ + 3H₂

This equation indicates that 2 moles of aluminum react with 6 moles of hydrochloric acid, producing 3 moles of hydrogen gas. Accurate stoichiometric calculations require the reaction to be balanced, ensuring the conservation of mass and atomic counts.

Application of Stoichiometry to Quantitative Analysis

In this experiment, aluminum reacts with hydrochloric acid to produce hydrogen gas, which can be measured volumetrically using a graduated cylinder submerged in water. The amount of hydrogen gas generated is directly related to the amount of aluminum reacted, allowing us to back-calculate the aluminum content through standard curves.

The process involves converting mass of aluminum to moles, using the molar mass (26.98 g/mol for aluminum), and then calculating the moles of hydrogen gas released, utilizing the stoichiometric ratio derived from the balanced reaction equation. This allows the determination of the aluminum mass based on the volume of hydrogen collected, considering the ideal gas law: PV=nRT.

Standard Curve Preparation and Data Collection

Initial experiments involve reacting known masses of pure aluminum with hydrochloric acid and measuring the resulting hydrogen gas volume. Plotting the volume of hydrogen produced (mL) versus the mass of aluminum consumed (g) yields a standard curve, which serves as a calibration aid for analyzing commercial aluminum samples.

Multiple trials with different aluminum masses improve the accuracy of the calibration curve, and the linear regression equation obtained (e.g., y = mx + b) enables estimation of aluminum content in unknown samples by measuring the hydrogen volume and applying the equation.

Experimental Procedures

The procedure begins with setting up the hydrogen collection apparatus, involving water displacement with a graduated cylinder, tubing connections, and a stirring mechanism ensuring complete reaction. Aluminum wire or foil samples are weighed accurately using a digital scale, then placed in a flask that is filled with hydrochloric acid. The reaction is initiated by stirring, and the evolution of hydrogen gas is recorded via the displaced water level in the graduated cylinder.

Pure aluminum samples are tested initially to create the standard curve by plotting hydrogen volume against known aluminum mass. Commercial foils, Reynolds Wrap and Great Value, are then tested similarly, with their hydrogen volumes measured for each sample. Multiple samples are analyzed to ensure reliability, and the aluminum content is calculated using the standard curve equation, adjusting for the molar masses and the reaction stoichiometry.

Data Analysis and Calculation of Aluminum Content

Using the collected data, a linear regression analysis provides the best fit line for the standard curve. The equation of the line relates hydrogen volume to aluminum mass, allowing the calculation of the aluminum content in commercial samples based on hydrogen measurements. Applying the ideal gas law (PV=nRT), the volume measurements are converted to moles of hydrogen, and from the stoichiometry, to moles—and subsequently the mass—of aluminum in each sample.

This method not only allows for precise quantification but also demonstrates the reliability of using gas-volume measurements in chemical compositional analysis. The accuracy of results depends on careful calibration, reaction completeness, and precise measurement.

Conclusion

The experiment effectively illustrates the application of stoichiometry and gas laws in real-world material analysis. Quantifying aluminum content in commercial foils helps ensure product consistency and quality. Moreover, understanding the principles behind reaction balancing and gas-volume measurements enhances the comprehension of chemical analytical techniques in industrial and research settings.

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