Chem 2 Inital Lab Report #1 PDF

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This was a rough draft of my final submission. I earned an A in this class....

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Calorimetry: Determining the Accuracy of a Styrofoam Calorimeter

Danielle Curtis CHM 2046L Section 905 TA: Sami Abdulkadir September 14th, 2016

Introduction Very few people actually pay attention to how heat transfer affects their daily lives. Whether an individual is using a thermos or an instant cold pack, the average person often faces many encounters with products that were designed based on common chemistry principles, like thermochemistry1. Product developers and scientists make use of different chemical reactions, like exothermic or endothermic reactions, in order to design products like the ones mentioned above1. One way to measure heat transfer from a system to its surroundings is through the use of a calorimeter. A calorimeter is defined as a well-insulated piece of equipment that can hold a chemical reaction or two substances that are being mixed, in order for the amount of heat released or absorbed to be measured1. Many academic institutions use calorimeters in the lab and these calorimeters can be man-made or manufactured. Man-made calorimeters are often constructed from Styrofoam, and while many institutions claim these Styrofoam calorimeters are reliable and accurate, many students are skeptical of this1. The objective of this experiment is to construct a Styrofoam calorimeter, gather empirical data to inform decisions about effectiveness and compare its performance to that of an already manufactured calorimeter1. Moreover, another objective of this experiment is to determine the heat capacity of both calorimeters and determine the enthalpy of chemical reactions: an acid base reaction that combines acetic acid (CH3COOH) and sodium hydroxide (NaOH), and a redox reaction between solid magnesium (Mg) and sodium hydroxide (NaOH)1. Understanding thermal energy exchange and how calorimeters operate is important because it has many chemical and practical applications. For instance,

calorimetry is often considered one of the most important experimental techniques because it is the only experimental method that allows for direct measurements of an assortment of physical and chemical reactions2. In regards to practical applications, understanding heat exchange is important because it explains why an individual’s body loses heat in cold temperatures or why one may burn their hand on a hot cup of coffee or on a hot pot. The proposed experimental procedure below is effective in addressing the objectives stated above because they allow for enough data to be collected so that an accurate comparison can be made between the two calorimeters. Moreover, it also allows for enough trials conducted so that the heat capacity of both calorimeters and the determined enthalpy of each reaction is as accurate as possible. Methods Construction of the Styrofoam Calorimeter and Set-Up of the Manufactured Calorimeter Proper personal protective equipment was worn and hair was tied back. To construct the Styrofoam calorimeter, two Styrofoam cups were obtained and one was placed inside the other. A piece of cardboard was obtained and a circle the size of the Styrofoam cup opening was cut out using scissors. The circle was placed in the opening of the cup ensuring that the entire cup was sealed shut. One small hole was cut out in the middle of the circular piece of cardboard so that a thermometer could be inserted. It was ensured that the opening was small enough that the edges sealed the thermometer in so that no heat would escape. A mercury thermometer was placed in the small opening. Caution was used when handling the mercury thermometer because if broken, the mercury could have escaped and mercury can be hazardous in cases of skin or eye

contact, and cases of inhalation or ingestion3. To set up the manufactured calorimeter, the beaker inside the calorimeter and the electronic thermometer were rinsed with distilled (DI) water to prevent cross contamination. The electronic thermometer tip was placed in the small hole on the lid of the calorimeter. Testing Calorimeters with Hot/ Room Temperature Water to Determine Heat Capacity The mass of the Styrofoam calorimeter and manufactured calorimeter was measured with an electronic scale and recorded. A 100 mL beaker was filled with 50 mL of DI water and heated to approximately 60C. The temperature was measured and recorded. A 100 mL beaker was filled with 50 mL of room temperature DI water. The temperature was measured and recorded. The 50 mL of room temperature water was added to the Styrofoam calorimeter. The 50 mL of hot water was added to the room temperature water in the Styrofoam calorimeter next. This was done to ensure that the hot water did not splash due to the fact that hot water can cause burns if it comes in contact with exposed skin. The mixture of room temperature and hot water was stirred 5 times. The thermometer was inserted and temperature recordings were taken every 20 seconds for a total of 4 minutes (or until the temperature remained constant for an extended period of time). The data was recorded in a chart. The above steps were repeated for 2 more trials (a total of 3). The above steps were repeated using the manufactured calorimeter. The data collected was used to find T. T and the specific heat of water was used to find the change in energy between the hot and room temperature water. E of hot water was subtracted form E of room temperature water to determine how much of the heat was transferred from to each calorimeter. When the trials were done the excess water was disposed of in the sink.

Determining the Enthalpy of a Chemical Reaction: CH3COOH and NaOH The Styrofoam and manufactured calorimeter were cleaned out with DI water to prevent cross contamination. Two 100 mL beakers were obtained and rinsed with DI water. One beaker was filled with 25 mL of NaOH and the other beaker was filled with 25 mL of CH3COOH. Caution was taken when handling NaOH and CH3COOH because both substances can cause irritation in cases of skin or eye contact and cases of inhalation or ingestion4,5. The temperature of the NaOH and CH3COOH was taken with the electronic thermometer and recorded. The 25 mL of NaOH was added to the Styrofoam calorimeter first, then the 25 mL of CH3COOH was added next. The Styrofoam calorimeter was sealed shut and the mixture was mixed about 5 times. The thermometer was inserted into the Styrofoam calorimeter and the temperature was recorded every 20 seconds for about 3 minutes (or until the temperature remained constant for an extended period of time). The data was recorded in a chart. The above steps were repeated for 2 more trials (a total of 3). The above steps were repeated using the manufactured calorimeter. The recorded temperatures and specific heat capacity were inputted into the equation q=McT to calculate the enthalpy of the reaction (see results for a sample equation). At the end of the experiment the liquid waste was disposed of in the appropriate waste disposal container. Determining the Enthalpy of a Redox Reaction: Mg and CH3COOH The Styrofoam and manufactured calorimeter were cleaned out with DI water to prevent cross contamination. One 100 mL beaker was obtained and rinsed with DI water. 0.25 g of solid magnesium (Mg) shavings was obtained. Caution was taken when handling Mg because this substance can cause slight irritation in cases of skin and eye

contact or cases of inhalation and ingestion5. The 100 mL beaker was filled with 25 mL of CH3COOH. The temperature of the CH3COOH was taken with the electronic thermometer and recorded. The 25 mL of CH3COOH was added to the Styrofoam calorimeter. The 0.25 g of Mg was then added to the Styrofoam calorimeter. The lid of the calorimeter was sealed shut and the mixture was stirred approximately 5 times. The thermometer was inserted into the Styrofoam calorimeter and the temperature was recorded every 20 seconds for approximately 3:20 minutes (or until the temperature remained constant for an extended period of time). The data was recorded in a chart. The above steps were repeated for 2 more trials (a total of 3). The above steps were repeated using the manufactured calorimeter. The recorded temperatures and specific heat capacity were inputted into the equation q=McT to calculate the enthalpy of the reaction (see results for a sample equation). At the end of the experiment the liquid waste was disposed of in the appropriate waste disposal container. Results Table #1: Heat Capacity of Calorimeters with Water

Styrofoam Calorimeter mhot water= 46.523 g mcold water= 48.303 g

Trial #1 Troom temp water = 21.9C Thot water = 60C Final Tmixture = 37C

Trial #2 Troom temp water= 21.7C Thot water = 64C Final Tmixture = 40.8C

Troom temp water = 21.9C Thot water = 68C Final Tmixture = 38C

Trial #3 Troom temp water = 22.2C Thot water = 62.1C Final Tmixture = 40.1C

Troom temp water = Troom temp water = 23.4C 20.9C Thot water = 60C Thot water = 60C Final Tmixture = Final Tmixture = 38.1C 41.2C Table 1: This table shows the initial temperatures of the room temperature and hot water, Manufactured Calorimeter mhot water= 46.523 g mcold water= 48.303 g

as well as the final temperature of the two substances mixed together.

Table #2: Acid-Base Reaction Trial #1 Trial #2 Trial #3 Tacid= 21.4C Tacid= 21.4C Tacid= 21.4C Tbase = 22.6C Tbase = 22.6C Tbase = 22.6C Final Tmixture = Final Tmixture = Final Tmixture = 37.4C 37.0C 36.1C Tacid= 21.7C Tacid= 21.7C Tacid= 21.7C Manufactured Tbase = 22.7C Tbase = 22.7C Tbase = 22.5C Calorimeter Final Tmixture = Final Tmixture = Final Tmixture = 42.4C 41.3C 41.4C Table 2: This table shows the initial temperature of the acid and base, as well as the final Styrofoam Calorimeter

temperature of the two substances mixed together. Table #3: Redox Reaction Trial #1 Trial #2 Trial #3 mMg= 0.25 g mMg= 0.25 g mMg= 0.25 g Tacid = 21.4C Tacid = 21.4C Tacid = 21.4C Final Tmixture = Final Tmixture = Final Tmixture = mMg= 0.25 g mMg= 0.25 g mMg= 0.25 g Manufactured Tacid = 21.4C Tacid = 21.4C Tacid = 21.4C Calorimeter Final Tmixture = Final Tmixture = Final Tmixture = 45.2C 47.4C 49.9C Table 3: This table shows the initial temperature of the acid and the mass of Mg used, as Styrofoam Calorimeter

well as the final temperature of the two substances mixed together.

It was found that the Styrofoam calorimeter typically yielded a lower final temperature for the mixture then the manufactured calorimeter did. For example, in the second table the final temperature in the Styrofoam calorimeter for each trial was 37.4C, 37.0C and 36.1C. Where as, the final temperature in the manufactured calorimeter was 42.2C, 41.3C and 41.4C. The results were similar for table 1, however trial 2 was an exception. For trial 2 in table 1, the final temperature in the Styrofoam calorimeter was 40.8C and the final temperature for the manufactured calorimeter was 38.1C. This mean for this trial the final temperature in the Styrofoam calorimeter was actually higher then

the final temperature in the manufactured calorimeter. The data collected for the redox reaction depicted in table 3 was inconclusive because we did not record data for both calorimeters, only for the manufactured calorimeter.

Sample Calculations Equation for Specific Heat Q=mcT Thot=30 Tcold=16.1 Qhot=(46.5)(4.181)(30)=5832.495 Qcold=(48.3)(4.181)(16.1)=3251.27103 Qcenergy gained by cup=5832.5-3251.3=2581.2 Qc=cT 2581.2=c(16.1) c=160.3Jg-1k-1 ***This calculation was used for each trial in each reaction and then averaged to find the average heat capacity Discussion The above results are important to the report because the final temperature found when two substances were mixed together allows for the heat capacity to be determined. For example, this is done in one calculation by calculating the “Q” of the hot and cold water, subtracting them from each other to get “Qc”(energy gained by the cup) and then plugging in that value into the Qc=cT equation to isolate for “c”.

It was found that when tested that both calorimeters were fairly similar but the manufactured calorimeter was slightly more accurate and reliable. Moreover, although the Styrofoam calorimeter was slightly less reliable the standard deviations calculated concluded that the margin of error for the Styrofoam calorimeter was minimal. Therefore, proving that students should not be skeptical about using Styrofoam calorimeters in the lab because the margin or error is small enough to not skew potential data or results a significant amount, rendering it negligible. Moreover, it also proves that Styrofoam calorimeters are just as effective as manufactured ones. Some sources of error that could have occurred in this experiment were that the measurements may have been inaccurate. For example, when recording the temperature the group did not wait the same amount of time each trial for the temperature to reach equilibrium when the two substances were mixed together. Moreover, this could have potential skewed the data resulting in inaccurate findings. Additionally, for trial 1 in table 1 a mercury thermometer was used to record the change of temperature, as opposed to the electronic thermometer that was used for every other trial. This affects the results collected because the mercury thermometer often results in user error when attempting to read it and is often less accurate or reliable then the electronic thermometer. Finally, another source of error was that the hot water in test one was not always heated to the same temperature for each trial. For example, trial one with the Styrofoam calorimeter was heated to 60C where as trial two was heated to 64C. This affects the data because a hotter initial temperature for the water will affect the final temperature for when the two substances were mixed together. In order to minimize sources of error next time, better pre-planning is required to minimize any last minute confusion in regards to calculations.

Also, being consistent throughout the experiment is imperative to keep the results as accurate as possible. Conclusion Conclusively, it was found that based on the tests that were performed and the results that were gathered, that both calorimeters were fairly similar but the manufactured calorimeter was slightly more accurate and reliable. However, due to the sources of error established in the discussion, it can be assumed that the calorimeters were even more similar than the data collected depicts. Moreover, the margin of error for the Styrofoam calorimeter was minimal and it was established by the group that a margin of error this small was not enough to skew potential data or results a significant amount. Therefore, proving that students should not be skeptical about the use of Styrofoam calorimeters in class because they are just as effective as manufactured ones. Research Connection The results and skills learned through this experiment can be applied to real life scenarios. For example, professors from the Yale University School of Medicine were conducting a study on the effects of insulin on the disposal of intravenous glucose6. The study was carried out by using the euglycemic insulin clamp technique on 24 normal patients6. The results collected suggested that the fact that a higher dose of insulin further stimulated glucose metabolism was primarily the result of an increase in glucose storage by peripheral tissues, such as muscle6. Moreover, in order to determine the relative contributions of glucose oxidation versus glucose storage by peripheral tissues following hyperinsulinemia, a euglycemic insulin clamp study combined with indirect calorimetry was performed6. Indirect calorimetry equipment differs from the calorimetry equipment

used in the lab in the sense that an indirect calorimetry is a technique used to measure inspired and expired gas flows, volumes and concentrations of O2 and CO2, allows measurements of oxygen consumption and carbon dioxide consumption6. Although the two differ, it relates to the experiment conducted in the lab because both require the basic understanding of how an exchange between system and surroundings works. Moreover, a basic understanding of how calorimeters operate is also a necessity in order to carry out both experiments. Without this basic knowledge this groundbreaking experiment would never have been able to be conducted and the important data collected would never be available, potentially risking many peoples’ lives. References [1]Anderson, L; Figueroa, J; Lykourinou, V. General Chemistry II Lab Manual; University of South Florida: Tampa, FL, 2016; P. 15- 21 [2]Piekarski, H. Calorimetry: An Important Tool in Solution Chemistry; Thermochimica Acta [online] 2004, 1, 13-18 [3]Mercury; MSDS No. 7439976 [online]; Science Lab.com: 14025 Smith Rd. Houston Texas 77396, 10/09/2005. URL: http://www.sciencelab.com/msds.php?msdsId=9927224 (accessed September 13 2016) [3]Sodium Hydroxide; MSDS No. 1310732 [online]; Science Lab.com: 14025 Smith Rd. Houston Texas 77396, 10/09/2005. URL: http://www.sciencelab.com/msds.php? msdsId=9924998 (accessed September 13 2016) [4]Acetic Acid; MSDS No. 7732185 [online]; Science Lab.com:14025 Smith Rd. Houston, Texas 77396, 10/09/2005. URL:

https://www.sciencelab.com/msds.php?msdsld=9925518 (accessed September 13 2016) [5]Magnesium; MSDS No. 7439954 [online]; Science Lab.com:14025 Smith Rd. Houston, Texas 77396, 10/09/2005. URL: http://www.sciencelab.com/msds.php?msdsId=9924535 (accessed September 13 2016) [6]DeFronzo, R; Jacot, E; Jequier, E; Maeder, E; Wahren, J; Felber, J.The Effect of Insulin on the Disposal of Intravenous Glucose: Results from Indirect Calorimetry and Hepatic and Femoral Venous Catherization; Diabetes [online] 1981, 12, 1...