Chm 145L Revised 1/24/20 Stoichiometry Of Vinegar And Baking ✓ Solved

Chm 145lrevised 1 24 20stoichiometry Of Vinegar And Baking Sodaintrodu

In chemistry, reactions are written as equations with chemical symbols, with reactants on the left and products on the right. The law of Conservation of Mass states matter is neither created nor destroyed, so chemical equations must be balanced, ensuring the number of atoms per element is equal on both sides. Stoichiometry describes the quantitative relationships between reactants and products in a chemical reaction.

The objective of this laboratory is to determine the correct chemical reaction between sodium hydrogen carbonate (baking soda, NaHCO₃) and acetic acid (vinegar, CH₃COOH). The experiment will use stoichiometric calculations based on the amount of carbon dioxide produced to identify which of three proposed balanced reactions correctly describes the process:

• Reaction A: CH₃COOH (aq) + NaHCO₃(s) → 2 CO₂(g) + CH₂O(aq) + Na⁺(aq) + 3 H⁺(aq)
• Reaction B: CH₃COOH (aq) + NaHCO₃(s) → CO₂(g) + H₂O(l) + NaCH₃COO(aq)
• Reaction C: CH₃COOH (aq) + 2 NaHCO₃(s) → CO₂(g) + Na₂CO₃(aq) + H₂O(l) + 2 CH₂O(aq)

The experiment involves reacting a known amount of sodium bicarbonate with excess vinegar, measuring the mass loss to determine the amount of CO₂ generated, and analyzing the mole ratio of NaHCO₃ to CO₂. Different ratios correspond to different proposed reactions, allowing identification of the true chemical pathway based on experimental data.

Sample Paper For Above instruction

The reaction between acetic acid and sodium bicarbonate is a classic example of an acid-base and decomposition reaction. When these reactants combine, they produce carbon dioxide (CO₂), water, and a sodium acetate solution. The key to determining the correct reaction equation involves analyzing the mole ratios of reactants and products, primarily using the amount of CO₂ generated in the experiment.

Background and Significance

Understanding the reaction stoichiometry provides insights into chemical reactivity and helps in practical applications, such as baking, cleaning, and understanding environmental processes. The reaction's main observable is rapid CO₂ evolution, visible as bubbling or fizzing. Determining the precise products involved in this reaction is essential for understanding chemical mechanisms and confirming theoretical predictions.

Methodology

The experiment uses a simple setup: reacting a measured amount of sodium bicarbonate with excess vinegar and measuring mass loss. This indirect method involves weighing the reaction mixture before and after the reaction to calculate the CO₂ produced, with corrections for CO₂ solubility in water. The procedure follows precise steps: weighing, reacting, weighing again, and calculating molar quantities based on known molar masses.

Calculations and Data Analysis

Calculations involve converting measured masses of sodium bicarbonate to moles by dividing by molar mass and determining moles of CO₂ via mass difference. Adjustments account for dissolved CO₂ using an experimentally determined correction factor. By comparing the ratio of moles of NaHCO₃ to CO₂, the correct reaction pathway is identified, following the expected ratios for each proposed reaction: 1:2 for Reaction A, 1:1 for Reaction B, and 2:1 for Reaction C.

Results and Interpretation

Data collected across multiple trials are analyzed to find the average mole ratios, considering experimental uncertainties and possible deviations within 20%. The most consistent ratio with theoretical expectations supports the correct reaction equation. The findings typically indicate that Reaction B (producing a 1:1 ratio of NaHCO₃ to CO₂) aligns with experimental outcomes, thereby confirming that acetic acid reacts with sodium bicarbonate to produce carbon dioxide, water, and sodium acetate.

Critical Discussion

The experiment demonstrates the law of conservation of mass and stoichiometric principles in practice. Errors such as incomplete reaction, measurement inaccuracies, or CO₂ dissolution influence the results. Improving experimental precision, such as using more accurate balances, controlling temperature, and ensuring complete reaction, can enhance data reliability.

Conclusion

Based on the calculated molar ratios, the analysis supports Reaction B as the correct chemical equation, aligning with the theoretical understanding of acid-base reactions involving sodium bicarbonate and acetic acid. This experiment exemplifies how stoichiometry can be applied practically to identify chemical reactions and quantify reaction components.

Post-Lab Questions

1. Yes. The experiment applies the conservation of matter concept by measuring mass before and after the reaction, assuming that the total mass remains constant aside from the escaped CO₂.
2. Sources of error include measurement inaccuracies, incomplete reactions, and CO₂ dissolution. Improvements involve ensuring thorough mixing, using higher precision balances, controlling temperature, and accounting for dissolved gases more precisely.
3. The molar mass of H₂SO₄ is 98.08 g/mol. To react with 50 g of H₂SO₄, the required amount of NaOH can be calculated based on the balanced reaction: NaOH + H₂SO₄ → Na₂SO₄ + H₂O. The molar ratio is 2:1, so:

1. Moles of H₂SO₄ = 50 g / 98.08 g/mol ≈ 0.51 mol.

2. Moles of NaOH needed = 2 × 0.51 mol = 1.02 mol.

3. Mass of NaOH = 1.02 mol × 40.00 g/mol ≈ 40.8 g.

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