Wal Socw6121 06 A En Ccmp41stoichiometrylab Introduction ✓ Solved

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A balanced equation, like a recipe, should allow us to predict how much product we are able to collect. The relationship between substances in a balanced chemical equation is called stoichiometry. In this lab we are going to look at a very simple reaction, with a very predictable amount of product, or “theoretical yield." In a reaction involving more than one substance reacting, we may find that one substance controls the amount of product, and this is because it is largely consumed before the other. This substance is termed the limiting reactant. When it is gone from the reaction mixture, no more product may be made and the reaction stops. Even if we continue to add more of the other reactants, there can still be no reaction. The reacting substances that are not consumed are said to be “in excess.” In our reaction, we are able to compare the amount of product that we are creating because it is a gas. We will collect the gas produced and attempt to compare the yields, based on the conditions.

As you perform the experiment, look for reasons that the amount of gas may not be an accurate reflection of the reaction. As always, when mixing materials, especially when gases are involved, you will want to wear adequate PPE. Prepare your notebook. When the lab is complete your lab notebook should include the following: 1. Include Stoichiometry Lab in the Table of Contents 2. Write the title of the lab on the top of the page. 3. Date/number the page. 4. Record the Purpose of Experiment in your own words. 5. Indicate PPE required while performing the lab. 6. Prepare your notebook to record observations. 7. Complete the post-lab question.

Stoichiometry Activity: In this lab we will study limiting reactants, excess reactants and calculations from a balanced chemical equation. We will also be looking for errors that occur while performing the reaction. Materials/Equipment needed: Lab kit bag, 20 oz (around 600mL) water bottle or soda bottle, 100 mL graduated cylinder.

Purpose: To make carbon dioxide from NaHCO3 and HC2H3O2 and to calculate the theoretical yield and limiting reagent for each.

Procedure: In this experiment you will 1) Label the packets of NaHCO3 in your lab kit bag: Experiment 1, Experiment 2, Experiment 3. Record the masses on each labeled packet of NaHCO3 in your Data Table 1. 2) Record the volumes used for each trial in the Data Table 1. 3) Experiment 1... 4) Experiment 2... 5) Experiment 3... Compare the balloons. Order the trials by the size of the balloon from smallest (1) to largest (3).

Data Table 1 Experiment 1 Experiment 2 Experiment 3 Mass NaHCO3 (g) Volume H2O (mL) Volume 3% (0.55M) acetic acid (mL) Ranking of Collected Gas Volume (1-3, 1 being smallest). Processing your data Sample Calculations: For your sample calculations, show your work below for the first set of data collected. 1) Calculate the moles of NaHCO3 in your first packet. 2) The density of white vinegar... 5) What is the expected number of moles of carbon dioxide based on the amount of NaHCO3 used? 6) Based on the moles of acetic acid, what is the expected yield...? 7) Which reagent is the limiting reagent? 8) Finally, if we expect that there are 24.4 L = 1 mol of gas at room temp, what volume of CO2 should we have observed in each trial?

Conclusion: Did your observations match your expectations? Explain why or why not. Think about the mL of CO2 predicted compared to the ranking of your balloon volumes. Be specific and include sources of error and the effect of the error on your yield of CO2(g).

Post-lab Problems: The problems are based on the following equation: Na2CO3(s) + 2 HCl(aq) --> 2 NaCl(s) + H2O(g) + CO2(g) 1) Calculate the mass (in grams) of NaCl produced by the reaction of 7.53 g Na2CO3 with an excess of concentrated (12.1M) HCl. 2) Determine the grams of water produced if 23.4 g of HCl is allowed to react with excess Na2CO3?

Paper For Above Instructions

The concept of stoichiometry is foundational in chemistry, enabling scientists and students to measure and predict the outcomes of chemical reactions accurately. The objective of this stoichiometry lab is to examine the relationship between reactants and products through the creation of carbon dioxide gas, using sodium bicarbonate (NaHCO3) and acetic acid (HC2H3O2) as reactants. Understanding the limiting reactant is essential, as it determines the maximum amount of product that can be generated in a reaction. This paper delves into the hypothesis established before experimentation, an overview of the methods used in the lab, the acquired data, and a comprehensive conclusion drawn from the findings.

Hypothesis

It is hypothesized that in the reaction between sodium bicarbonate and acetic acid, sodium bicarbonate will serve as the limiting reagent when introduced in lesser amounts compared to acetic acid, therefore controlling the amount of carbon dioxide produced. By observing the volume of gas collected during each experiment, it should be possible to correlate the theoretical yield of CO2 with the experimental outcomes.

Methods and Materials

In the stoichiometry lab, three experiments were conducted, each involving a distinct combination of sodium bicarbonate and acetic acid to yield carbon dioxide gas. The acid-base reaction can be represented by the balanced chemical equation:

NaHCO3 + HC2H3O2 → H2O(g) + NaC2H3O2 + CO2(g)

The items utilized for the experiment included sodium bicarbonate, vinegar (acetic acid), three labeled packets of NaHCO3 for each respective trial, a graduated cylinder for measuring liquids, and an empty water bottle topped with balloons to capture the produced gas.

Experimental Procedure

1. The sodium bicarbonate packets were labeled Experiment 1, Experiment 2, and Experiment 3 to differentiate the trials. The mass of NaHCO3 in each packet was recorded.

2. Each trial involved varying volumes of water and acetic acid:

  • Experiment 1: 25.0 mL water, 25.0 mL vinegar

  • Experiment 2: 20.0 mL water, 30.0 mL vinegar

  • Experiment 3: 30.0 mL water, 20.0 mL vinegar

3. The respective amounts were mixed and swirled in the water bottle, sealing it with a balloon to collect the evolved CO2 gas.

4. After each trial, the size of the balloon was observed and ranked according to the volume of gas produced.

Data Collection and Analysis

The results were recorded in a data table where the mass of NaHCO3, the volume of water and vinegar, and the ranking of gas volume collected were documented. Theoretical calculations followed to deduce the number of moles of reactants and products based on stoichiometric principles.

The molar mass of NaHCO3 (84.01 g/mol) and acetic acid (60.05 g/mol) were used to calculate the expected yield of CO2 in moles and subsequently in volume, considering that 1 mol of gas occupies 24.4 L at room temperature conditions.

Expected Results

From the calculations, it was anticipated that the yield of CO2 would vary with each experimental setup. In cases where NaHCO3 was the limiting reagent, the volume of CO2 produced would be less than predicted due to its depletion before the acetic acid could react completely.

Discussion

The outcomes of the experiment were critical in comparing theoretical yields versus observed gas volumes. Discrepancies such as gas leakage, inaccurate measurements, and reaction efficiency must have influenced the total volume collected. The experiments emphasized the importance of correct methodologies in achieving data validity.

Conclusion

The experiment successfully demonstrated stoichiometric principles in a practical setting and provided insights into limiting reagents and the significance of accurate experimental procedures. Through this lab, the limitations of expectations compared to real-life observations were highlighted, along with potential sources of error. Future experiments could focus on refining measurement techniques and controlling external variables to enhance accuracy.

References

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