Lab 2 chem

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University of Ottawa *

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3122

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Chemistry

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Dec 6, 2023

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In this laboratory experiment, our objective was to determine the most suitable chemical for cooling drinking water in a canister by at least 5°C within 5 minutes. The underlying theory guiding this experiment dictates that the introduction of salt into the calorimeter should trigger a cooling effect on the water within the canister. This cooling effect is a result of an endothermic reaction, prompted by the salt, which absorbs heat from the surrounding environment, including the can and the water it contains. Our task was to decide between two potential candidates: ammonium chloride (NH4Cl) and ammonium nitrate (NH4NO3). It was crucial that the chosen salt not only be effective for the task but also pose minimal health risks to consumers. Our research revealed that both chemicals have their respective safety considerations. Ammonium chloride can cause irritation upon skin contact or ingestion(1), while ammonium nitrate, in addition to being irritating to the skin, can potentially cause organ damage if ingested. Furthermore, ammonium nitrate is a powerful oxidizer that can exacerbate fires. (2) When ammonium chloride, a salt, is dissolved in water, it undergoes a process known as ionization, separating into its constituent ions: NH4+ and Cl-. The resulting ammonium ions (NH4+) exhibit weak acid properties, mildly acidifying the water by donating protons (H+) to form ammonia (NH3) and hydronium ions (H3O+)(3). However, this does not render the solution strongly acidic, as ammonium chloride is a weak acid and does not ionize completely. Interestingly, the dissolution of ammonium chloride in water is an endothermic process, absorbing heat and thereby causing a cooling effect. This property is exploited in practical applications such as first-aid cold packs.(4) Considering the safety and effectiveness of both ammonium chloride and ammonium nitrate, it is evident that ammonium chloride is the more appropriate choice for this experiment due to its lower risk profile. Nonetheless, it is important to conduct this experiment with the appropriate safety measures, including the use of personal protective equipment and adherence to relevant guidelines and regulations. 1. Ammonium Chloride; [En Ligne]; Cleartech: Saskatoon, SK, 13 juillet, 2018. https://www.cleartech.ca/ckfinder/userfiles/files/Ammonium%20Chloride%20CTI%20SDS.pdf.Ac cessed 9 Oct. 2023. 2. Ammonium Nitrate - Industrial Grade; SDS No. 300 [En Ligne]; PCS Sales: 30 avril, 2015. https://www.nutrien.com/sites/default/files/2018-01/SDS%20300%20Ammonium%20Nitrate%20 -%20Industrial%20Grade%20NA%2004302015%20%5BNutrien%5D.pdf.Accessed 9 Oct. 2023 . 3.“Adobe Acrobat: PDF Edit, Convert, Sign Tools.” Demonstrate Understanding of Chemical Reactivity Writing Excellence Answers to Ions and Conductivity, Chemistry 2.6 AS 91166 , chrome.google.com/webstore/detail/adobe-acrobat-pdf-edit-co/efaidnbmnnnibpcajpcglclefindmk aj. Accessed 9 Oct. 2023.

4.“Ammonium Chloride.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, pubchem.ncbi.nlm.nih.gov/compound/Ammonium-chloride#section=Safety-and-Hazards. Accessed 9 Oct. 2023. Procedure: 1- S'assurer d’avoir toutes les mesures de sécurité. 2- prendre la masse de la canette et trouver sa chaleur massique (JgK-1) 3- utiliser un bearché pour mesurer 100 ml d’eau avec une balance électrique et mettre ceci dans la canette. 4- ajouter 95 ml d’eau dans le calorimètre et placer la canette dans le calorimètre. 5 - mesurer X g de NH4Cl à l’aide d’une balance électrique . 6- préparer une collecte et donner de la température (C) en fonction du temps (s). 7-fermer le calorimètre en mettant le thermomètre dans la canette pour prendre la température initiale. 8- ouvrir le calorimètre et dissoudre Le NH4Cl dans l’eau qui entour le cannette (agiter la solution) 9- Commence le processus de collecte de données sur Labquest 2 pour 300 secondes pour des intervalles de 1 seconde. 10- Répéter ce processus 2 autre fois (pour une total de 3 essai et “enlever” ou “ajouter” plus de sel chaque essai ) 1.) Did you achieve your objective? The goal of this lab was to find the quantity needed of water and salt, to find the desired enthalpy for reducing the temperature of our product. In this experience, our fundamental goal was to make a product that could cool down the quantity of water in the can by using salt; and cool down 100cm3 of water by 5 degrees in 5 minutes. We achieved our goal in our second try of the experiment with our mechanism to cool down our product. 2.) Are there design flaws that affected your results? Yes, there were a couple of flaws that could have affected our results. For example, we couldn't tell for 100% sure if the salt was mixed well and dissolved in the water. The calorimeter was closed during the entire process of this experiment after the salt was added, to limit the loss of the temperature, so we have no visual indicator that tells us that the dissolving of the salt isn't finished. The calorimeter is also another flaw that could have affected our results. The calorimeter is supposed to limit the heat, to get release but the calorimeter we used wasn't fully isolated. This causes our results to be not precise or efficacy which leads to having places for errors. A calorimeter is isolated, to avoid heat transfer between the calorimeter and the environment so that it can measure the heat in the system only. It can't lose or gain heat between the calorimeter and the

environment. All of the calorimeters have holes in them to let the thermometer in to calculate the temperature, but ours could be moved around and not stay in place which indicated that there are spaces in the hole that are not being occupied which leads to heat loss. Finally, the liquid inside the canne needed to be uniformly cooled because this could affect our results. 3.) If so, how did you counter these flaws? To start, there are certainly some flaws due to the provided equipment that cannot be corrected. Despite being quite effective, our calorimeter is not a completely isolated system. We have made up for its shortcomings by limiting our temperature fluctuations. As an example, as soon as the solution was introduced, we immediately closed the calorimeter. Once the dissolving process had started, we had taken care to keep the system isolated. This allowed us to control the variations related to heat. For dissolving the salt inside the calorimeter we gently start shaking the calorimeter in a circular motion so that it can dissolve when the salt is introduced to it. We did this for a good 30 seconds to a minute to ensure that the salt was dissolved. Additionally, by gently moving the system, we ensure that the temperature inside the canne has been spread uniformly. 4.) If so, could you compensate for them? Yes, it is possible to make up for these shortcomings. As we mentioned earlier, these shortcomings are correctable. That said, we can make up for these shortcomings. We can stir the solution for a longer period of time because we are unable to predict when the dissolution will be completely complete. We had access to the can's internal temperature. Once the temperature stabilizes, the reaction is finished. As a result, we made up for it by mixing it slightly longer and basing our decisions on temperature variations. So, by producing the reactions with the least amount of human interference, we have made up for the calorimeter's imperfect isolation. Finally, we took the temperature during the entirety of the reaction to ensure that it was consistent throughout our can. Additionally, our thermometer can take temperatures at various locations within the cans when we lightly move the calorimeter. Finally, the heat is distributed evenly when we give the calorimeter enough time.

5.) If so, how did you factor the flaws into your explanation of your results? First, our results clearly show that our isolation is inadequate because the system gradually rewarms when we reach the coldest temperature. This means that the minimum temperature is not the final temperature, which should not be the case because the calorimeter should provide thermal isolation to prevent heat exchanges between the ambient environment and our system. Last but not least, it can be seen that the liquid in the can did not cool uniformly because to the large fluctuations we noticed when reading our temperatures over a very short period of time. In other words, when we moved the calorimeter to dissolve the sel, the can moved slightly and the temperature readings from the thermometer at various locations inside the canne were different. 6.) Is this a feasible method for the project? Considering our aim to conduct a thermochemical reaction, the use of a calorimeter was the most suitable approach for the experiment. The purpose of our lab was to assess heat variation during a reaction, which required an isolated system. As a result, there should be no exchange of heat or matter between the reaction system and its surroundings. Material loss is minimal since the reaction is a dissolution. Since dissolution is an endothermic reaction, it tends to cool its surroundings. The most effective way to conduct this experiment was to use a calorimeter, which ensured no heat exchange. Despite this, lab experiments can still be improved to improve accuracy. In order to mitigate the potential errors in the product's production and lab procedures, several solutions have been proposed. Additionally, conducting more trials of the product would be another significant improvement. In this way, the product would be thoroughly tested before being released to the general public. 7.) Would a different salt have a better effect? If so, state the salt and explain why? This product development process has caused several health, safety, and financial challenges. Financially speaking, the essential salt required for the operation of the product is cost-effective. The NH4Cl salt used to cool the drink is priced at only $84.88 per 500g, which is notably cheaper than the much more expensive ammonium nitrate (NH4NO3) at $100.14. Despite the financial advantages, significant health and safety concerns are associated with the use of the NH4Cl salt. In the event that this product is made available to the public, we may be held responsible for any health complications that occur. When NH4Cl salt comes into direct contact with the skin, it can pose a number of health risks. These include irritation to the nose, throat, and lungs, potential eye damage, and symptoms such as headaches, drowsiness, and confusion. Ammonium chloride may also cause kidney damage. This salt is commonly used in battery manufacturing, zinc coating and tinning, and fertilizer applications. Using it to cool a beverage for human consumption is understandably concerning, emphasizing the need for thorough safety considerations. 8.) What were your Safety/health/cost considerations?

This product development process has caused several health, safety, and financial challenges. Financially speaking, the essential salt required for the operation of the product is cost-effective. The NH4Cl salt used to cool the drink is priced at only $84.88 per 500g, which is notably cheaper than the much more expensive ammonium nitrate (NH4NO3) at $100.14. Despite the financial advantages, significant health and safety concerns are associated with the use of the NH4Cl salt. In the event that this product is made available to the public, we may be held responsible for any health complications that occur. When NH4Cl salt comes into direct contact with the skin, it can pose a number of health risks. These include irritation to the nose, throat, and lungs, potential eye damage, and symptoms such as headaches, drowsiness, and confusion. Ammonium chloride may also cause kidney damage. This salt is commonly used in battery manufacturing, zinc coating and tinning, and fertilizer applications. Using it to cool a beverage for human consumption is understandably concerning, emphasizing the need for thorough safety considerations. 9.) Is there a better way to do the experiment? Considering our aim to conduct a thermochemical reaction, the use of a calorimeter was the most suitable approach for the experiment. The purpose of our lab was to assess heat variation during a reaction, which required an isolated system. As a result, there should be no exchange of heat or matter between the reaction system and its surroundings. Material loss is minimal since the reaction is a dissolution. Since dissolution is an endothermic reaction, it tends to cool its surroundings. The most effective way to conduct this experiment was to use a calorimeter, which ensured no heat exchange. Despite this, lab experiments can still be improved to improve accuracy. In order to mitigate the potential errors in the product's production and lab procedures, several solutions have been proposed. Additionally, conducting more trials of the product would be another significant improvement. In this way, the product would be thoroughly tested before being released to the general public. 10.) Any other reasonable points may be discussed. - Predict a descending graph We took the time to make certain predictions about the curve generated by our results. To begin, the graph will deal with temperature (in degrees celsius) versus time (in seconds). The benign of the curve will begin looking stabled at the top before the ammonium chloride starts dissolving. When it starts, the temperature will go down meaning the graph will also go the same way. The product will become cooler because when ammonium chloride is introduced to water, it goes under an endothermic reaction. So the graph will keep going down until it reaches a stable momentum that will tell us our final temperature.

- Explain our results according to the table and the graphs The experimental data were compiled into a well-organized table (see referred Tables). In order to make the table easier to interpret, we decided to use time intervals of 50 seconds since each test included several hundred points of data. Two key values in our table are the initial and final temperatures. We calculated the temperature variation by subtracting the final temperature from the initial temperature to achieve our target of a -5°C change. Our liquid experienced a temperature shift as a result of this. Note that the final temperature listed may not be the lowest temperature reached during the experiment. In order to ensure complete dissolution, we allowed some additional time, which may have affected the final temperature. - Were the results obtained in agreement with the planned results? The outcomes of our experiment were consistent with our initial expectations. The recorded temperature variations for each test demonstrated a decrease of roughly 5°C. The initial test exhibited the least temperature variation, which was anticipated as it represented the basic or control reaction. In subsequent tests, we implemented changes such as altering the mass of salt or the volume of water in the calorimeter. These modifications led to temperature variations that were approximately -4°C, aligning more closely with our target. Therefore, the success of our experiment is evident in the results we recorded, as they accurately reflected our intended outcomes. Conclusion : In short, we succeeded in developing a product capable of cooling by 5 degrees Celsius in just 5 minutes in our second try. To achieve this, we used around 18 g of ammonium chloride (17.86 g) as the salt and 95 g of water in the calorimeter. This mixture was applied to a can containing 100 g of water, triggering an endothermic reaction. Table 1: Variable identification Dependent variables Independent variables Controlled variables -Reaction speed -Enthalpy -Temperature -Heat capacity -Volume -Time

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