Lyceum of the Philippines University - Laguna International School Explorations in Thermodynamics: Calorimetry, Specific Heat & Neutralization Del Valle, Alyssa L. Manuel, Robin Piolo M. Motas, Hannah Faye A. Pagaduan, Mark Gerald N. Ricablanca, Princess Jane D. Santos, Claude Jayson U. Seleteria, Richel B. Torres, Khim Harold O. GENCHEM 2 11 – Kingston Group 3 April 23, 2018 _______________________________ 1 A scientific paper submitted in partial fulfillment of the requirements in General Chemistry 2 Laboratory under Mr. Jeoffrey Sanga - Delos Reyes, 2nd sem., 2017 - 2018. Page 1 Lyceum of the Philippines University - Laguna International School ABSTRACT This experiment was done to discover more about heat transfer in regards to the law of conservation of energy. The students observed that the heat will increase at first, but it will decrease after some times. This experiment allowed us to derive three different values related to heat transfer inside a calorimeter (Styrofoam cup). The first part allowed us to calculate the mass and temperature of cold water and hot water using calorimeter constant. We did this by following a simple procedure of heating up the water and then transferring it into a Styrofoam cup containing cold water. By observing and recording the temperature changes in both the water (cold and hot) we were able to determine the calorimeter. This process can be categorized as Exothermic reaction, because this releases energy during the process. The calorimeter constant of the 50.0mL distilled water was determined based on the data collected from the experiment. Major findings showed that the calorimeter constant is 35.36 J/°C. For the heat of solution, calcium chloride and urea was used for the experiment. The students then recorded the temperature of the solution. The students also determined the heat of neutralization between sodium hydroxide and hydrochloric acid. After recording, the students then observed that the temperature of the mixture at first became warm that reaches into 40˚C but when the time goes at 30-45 seconds the temperature changes and remained at 43˚C until it reaches the time of 5 minutes. Keywords: calorimeter, heat, neutralization, temperature INTRODUCTION One of the timeliest scientific observations made by humans must have been the warmth provided by fire, and since that time the unexpected utility of heat as a tool has contributed to many of the most profound technological advances in humanity’s history. Page 2 Lyceum of the Philippines University - Laguna International School The science of heat flow, or more generally energy flow, is called thermodynamics. Many of the fundamental foundations of thermodynamics have been deliberated in our lectures on gas laws and the kinetic molecular theory of gases where we learned that heat and kinetic energy (the energy of motion) of gaseous atoms/molecules are equivalent. Now we are ready to turn our attention to subtler aspects of thermodynamics relating to thermal energy being extracted from or stored within a wider array of chemical compounds than gases. In this set of experiment, we will focus our attention upon one particular area of thermodynamics, namely calorimetry, is the science or act of calculating alterations in state variables of a body for the resolution of deriving, the heat transfer connected with changes of its state due, for example, to chemical reactions, physical changes, or phase transitions under quantified restrictions. Calorimetry is performed with a calorimeter (Buchholz 2001). The Calorimeter is the method of measuring the heat of chemical reactions or physical changes as well as heat capacity. The container we use as a calorimeter should thermally insulate the matter we’re interested in studying, it should prevent matter from entering or exiting once our measurement has begun, and it should allow for easy measurement of temperature changes. A coffee cup calorimeter is a constant pressure calorimeter. As such, the heat that is measured in such a device is equivalent to the change in enthalpy. A coffee cup calorimeter is normally used for solution based chemistry and as such commonly encompasses a reaction with diminutive or no volume change. (see Figure 1). Page 3 Lyceum of the Philippines University - Laguna International School Here is a coffee cup and its parts: Source:https://ch301.cm.utexas.edu/section2.php?target=thermo/thermochemistry/coffeecup-calorim.html Experimentally, measuring heat flows is somewhat difficult. We use thermometer to measure changes in temperature that can be operated as indirect measures of heat flow. In order to precisely relate measured temperature changes to the flow of particular amounts of thermal energy, a proportionality constant that relates these two quantities called the heat capacity. The Specific Heat Capacity is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The connection between heat and temperature change is usually expressed in the form shown below where c is the specific heat. On the other hand, the Law of Page 4 Lyceum of the Philippines University - Laguna Page International School 5 Conservation of Energy states that the whole energy of an insulated system remains constant, it is said to be preserved over time. This law means that energy can neither be produced nor destroyed; rather, it can only be converted from one form to another. Most of the chemists use a technique called calorimetry to regulate the specific heat of a substance. Calorimetry, or the measurement of heat transfer, is based on the Law of Conservation of Energy. This law states that energy is not produced nor destroyed; it is only converted from one form to another. Mathematically, the proportionality can be expressed as shown in equation 2.1: qrxn qsolution qcalorimeter qrxn (msolutioncwater T ) Ccal T ΔΗ solution 1 kJ 1000 J molsolute qrxn Where c is the specific heat capacity (in J/(g ˚C)), q is the quantity of thermal energy released/absorbed (in J), m is the mass of the sample (in g), and ∆T is the change in temperature (in ˚C), which is taken as Tfinal-Tinitial for the sample. Since specific heat capacities are positive constants for a given material, heat flow is directly proportional to changes in temperature. Thus if the change in temperature (∆T) is positive, then q is also positive indicating the absorption of heat by the sample (an endothermic process). Alternatively, if ∆T is negative then q is also negative indicating the loss of heat by the sample (an exothermic process). The Heat of neutralization is the change in heat that happens when one equivalent of an acid and one equivalent of a base undergo a neutralization reaction to form water and salt. It is defined as the energy released with the formation of 1 mole of water. Lyceum of the Philippines University - Laguna International School qcalorimeter qHCl q NaOH 0 qrxn [Ccal ΔTcal mHCl cwater ΔTHCl mNaOH cwater ΔTNaOH ] The study was conducted at the PHL Building, 4th Floor, Lyceum of the Philippines – Laguna, April 13, 2018. This study aimed to conduct a successful experiment about Calorimetry. The specific objectives were: 1. to calculate the heat the neutralization between sodium hydroxide and hydrochloric acid is endothermic and exothermic. 2. to find out the heat released or changed in a reaction. 3. to learn how to measure Heat flow and, 4. to learn about Exothermic and Endothermic chemical reactions MATERIALS AND METHODS In the observation and procedure, calorimeter was used in measuring the heat effects and calorimetry. The heat neutralization between an acid and a base can be calibrated through calorimetry where an insulated tumbler serves as the calorimeter. The tumbler, being a good insulator, is assumed to have negligible contribution to the heat capacity of the entire calorimeter. Thus, the reaction will only exchange heat with the water inside the calorimeter. Page 6 Lyceum of the Philippines University - Laguna International School Figure 1. Calorimeter To begin with the determination of calorimeter constant, the calorimeter has been assembled using the coffee cup. 50.0 mL cold distilled water was placed into the Styrofoam cup. Using a separate beaker, the distilled water measuring another 50.0 mL was heated to about 70⁰C. While the water is heating, the temperature of the cold water in the calorimeter has been monitored for about 2-3 minutes to make sure that it has become constant and the temperature of the cold water was recorded. Next, the water in the beaker that has reached 70⁰C was just set aside for about 12 minutes then the temperature of the warm was also recorded. The lid of the calorimeter was quickly removed and the warm water has been poured into the cold water. The lid has been replaced immediately and the water was stirred for 30 seconds. The temperature of the mixed warm and cold water was monitored and recorded the highest temperature reached by the water. Page 7 Lyceum of the Philippines University - Laguna International School Figure 2. Measuring the distilled water with thermometer The calorimeter constant has been calculated for the calorimeter. Thema ss of the empty calorimeter together with the warm and cold water were computed as well as the final and initial temperature of it. Afterwards, the heat of the solution was computed. The distilled water measuring 50.0 mL was placed in the calorimeter and recorded the temperature. The calcium chloride weighing 5.00 g was placed into the calorimeter and then the lid was quickly replaced. The solution was stirred and the temperature has been determined. The procedure was repeated using the urea instead of calcium chloride. The Change in Enthalpy of solution in calcium chloride and urea was measure by using the data gathered and applying its formula. For the heat of neutralization, the materials that are needed to be used are Insulated tumbler which is the Styrofoam cup that was given, A 6 M HCl solution and 6 M NaOH solution, A digital thermometer and a 100 mL graduated cylinder. The estimated time frame of doing this experiment is around 20 minutes. The first thing that should be done before anything else is to put all the materials to be used on a safe place. To start the heat neutralization, the first thing that should be done is to measure 20mL of 6 M NaOH solution using 100 mL graduated cylinder and then after measuring Page 8 Lyceum of the Philippines University - Laguna International School the solution, put it into the beaker. After that, measure and record the initial temperature of the NaOH solution using digital thermometer. Figure 3. Measuring distilled water with NaOH Next is Measure 20mL of 6M HCl solution using also the graduated cylinder and then measure and record also the initial temperature of the 20mL 6M HCl solution using the digital thermometer just like what we do from the first step. Now, after measuring the initial temperature of the two solutions, the next procedure to be done is to pour the HCl solution into the tumbler to mix it with the NaOH solution. Cover the tumbler immediately and swirl it gently to mix the contents of the two solution. Then, after mixing the two solutions, ready a timer or a watch to measure its temperature every 15 seconds for 5 minutes. To do this, slightly lift the cover to insert the Page 9 Lyceum of the Philippines University - Laguna International School thermometer. Record the gathered data to the table that is given. Lastly, calculate the heat of neutralization from the data gathered. RESULTS AND DISCUSSION Results showed that styrofoam cups and styrofoam cover were used in the experiment, because it is a good insulator that prevents heat exchange with the environment. The students made sure that the cover is in place during the experiment so that the sytrofoam cover can provide adequate insulation for heat transfer measurements which enables the accurate determination of the heat involved in chemical processes and to determine the heat of neutralization and the heat of solution. Part A: Determination of Calorimeter Constant Given: ∆𝑇𝑐𝑎𝑙 = 17℃ 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 − 𝑚𝑒𝑚𝑝𝑡𝑦 𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 = 74.92𝑔 − 25.32𝑔 𝑚𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 = 49.6𝑔 ∆𝑇𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 = 17℃ 𝑚ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟+ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 − 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 𝑚ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 = 121.92𝑔 − 74.92𝑔 Page 10 Lyceum of the Philippines University - Laguna International School 𝑚ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 = 47𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 ∆𝑇ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 = −21℃ 𝑔℃ Solution: Ccal ΔTcal mcold cwater ΔTcold water mhotcwater ΔThot water 0 4.18 𝐽 4.18𝐽 𝐶𝑐𝑎𝑙 (17℃) + (49.6𝑔) ( ) (17℃) + (47𝑔) ( ) (−21℃) = 0 𝑔℃ 𝑔℃ 𝐶𝑐𝑎𝑙 (17℃) + (3524.576𝐽) + (−4125.66𝐽) = 0 𝐶𝑐𝑎𝑙 (17℃) − 601.084𝐽 = 0 𝐶𝑐𝑎𝑙 (17℃) 17℃ = 601.084𝐽 17℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ The Calorimeter constant is equal to 35.36 J/°C Part B: Heat of Solution Given: 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 + 𝑚𝐶𝑎𝐶𝑙2 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 49.6𝑔 + 5.00𝑔 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 54.6𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑎𝑙𝑢𝑒 = − 82.8 𝑘𝐽/𝑚𝑜𝑙 Page 11 Lyceum of the Philippines University - Laguna International School ∆𝑇 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ∆𝑇 = 26℃ − 36℃ ∆𝑇 = −10℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Solution: ∆𝐻𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑜𝑓 𝐶𝑎𝐶𝑙2 𝑞𝑟𝑥𝑛 = −[𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇) + 𝐶𝑐𝑎𝑙 ∆𝑇] 4.18 𝐽 𝐽 𝑞𝑟𝑥𝑛 = −[(54.6𝑔) ( ) (−10℃) + (35.36 )(−10°𝐶) 𝑔℃ °𝐶 𝑞𝑟𝑥𝑛 = −[(−2282.28 𝐽) + (−353.6 𝐽)] 𝑞𝑟𝑥𝑛 = −[−2635.88 𝐽] 𝑞𝑟𝑥𝑛 = 2635.88 𝐽 2635.88𝐽 × ∆𝐻𝐶𝑎𝐶𝑙2 = 1000𝐽 0.0451𝑚𝑜𝑙 ∆𝐻𝐶𝑎𝐶𝑙2 = 58.45 𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 %𝐸𝑟𝑟𝑜𝑟 = | 1 𝑘𝐽 𝑘𝐽 −82.8 𝑚𝑜𝑙 − 58.45 𝑚𝑜𝑙 𝑘𝐽 −82.8 𝑚𝑜𝑙 %𝐸𝑟𝑟𝑜𝑟 = 1.71% | × 100% Page 12 Lyceum of the Philippines University - Laguna International School The dissolution of calcium chloride is an endothermic process. With the use of calorimetry formula, we come up with the answer with positive sign. As we all know that if the answer is positive or if the q, which is the heat, is absorbed then it is an endothermic process so probably the process that has been found here is an endothermic process. Given: 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 + 𝑚𝑢𝑟𝑒𝑎 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 49.6𝑔 + 5.01𝑔 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 54.61𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑎𝑙𝑢𝑒 = 14.0 𝑘𝐽 𝑚𝑜𝑙 ∆𝑇 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ∆𝑇 = 26℃ − 24℃ ∆𝑇 = 2℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Solution: ∆𝐻𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑜𝑓 𝑈𝑟𝑒𝑎 (𝐶𝐻4 𝑁2 𝑂) 𝑞𝑟𝑥𝑛 = −[𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇) + 𝐶𝑐𝑎𝑙 ∆𝑇] 𝑞𝑟𝑥𝑛 = −[(54.61𝑔) ( 4.18 𝐽 𝐽 ) (2℃) + (35.36 )(2℃) 𝑔℃ ℃ 𝑞𝑟𝑥𝑛 = −[(456.5396 𝐽) + (70.72 𝐽)] Page 13 Lyceum of the Philippines University - Laguna International School 𝑞𝑟𝑥𝑛 = −[527.2596 𝐽] 𝑞𝑟𝑥𝑛 = −527.2596 𝐽 1 𝑘𝐽 ∆𝐻𝑢𝑟𝑒𝑎 = (−527.2596 𝐽) × 1000 𝐽 0.0834 𝑚𝑜𝑙 ∆𝐻𝑢𝑟𝑒𝑎 = −6.32 𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 𝑘𝐽 14.0 𝑚𝑜𝑙 − (−6.32 𝑚𝑜𝑙) %𝐸𝑟𝑟𝑜𝑟 = | 𝑘𝐽 14.0 𝑚𝑜𝑙 | × 100% %𝐸𝑟𝑟𝑜𝑟 = 1.45% The dissolution of urea is an exothermic process because as we conduct an experiment, by the use of calorimetry formula that we also used in the dissolution of calcium chloride, we found out that it releases heat. The answer we got has a negative sign. We already know that if the answer is negative or the q, which is the heat, is released or lose then it is an exothermic process so probably the process that has been found here is an exothermic process. Page 14 Lyceum of the Philippines University - Laguna Page International School 15 Part C: Heat of Neutralization Temperature versus Time 43,5 43 42,5 42 41,5 41 Ряд1 40,5 40 39,5 39 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 38,5 Table 1. Graph of Temperature Versus Time As shown in the graph above, the highest temperature attained by the mixture solution in the graph above is 43˚C and the lowest is 40˚C. As observed in the experiment, the temperature of the mixture reaches 40˚C at first but when the time goes at 30-45 seconds the temperature increases and stays at 43˚C until it reaches the given time of 5 minutes. The highest temperature attained by the mixture solution is 42°C. As observed, the temperature of the mixture solution remained at 42°C from the start until the end of the five minutes of temperature reading. The loss of energy to the Lyceum of the Philippines University - Laguna International School experiment’s surrounding will be less in the styrofoam cup because it is a good insulator that prevents. Error might occur when some heat escape from the cup. Some of the heat were absorbed by the water & the cup, and also escape when we did not close the cup correctly. Given: 𝑚𝐻𝐶𝑙 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+(𝑁𝑎𝑂𝐻+𝐻𝐶𝑙) − 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑁𝑎𝑂𝐻 𝑚𝐻𝐶𝑙 = 127.67𝑔 − 76.81𝑔 𝑚𝐻𝐶𝑙 = 50.86 𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑚𝑁𝑎𝑂𝐻 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑁𝑎𝑂𝐻 − 𝑚𝑒𝑚𝑝𝑡𝑦 𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑚𝑁𝑎𝑂𝐻 = 76.81𝑔 − 25.32𝑔 𝑚𝑁𝑎𝑂𝐻 = 51.49𝑔 ∆𝑇𝐻𝐶𝑙 = 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑇𝑓𝑖𝑛𝑎𝑙 ∆𝑇𝐻𝐶𝑙 = 25℃ − 43℃ ∆𝑇𝐻𝐶𝑙 = −18℃ ∆𝑇𝑁𝑎𝑂𝐻 = 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑇𝑓𝑖𝑛𝑎𝑙 ∆𝑇𝑁𝑎𝑂𝐻 = 25℃ − 43℃ ∆𝑇𝑁𝑎𝑂𝐻 = −18℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Theoretical Value: Page 16 Lyceum of the Philippines University - Laguna International School ∆𝐻𝑟𝑥𝑛 = −55.8 𝑘𝐽 𝑚𝑜𝑙 Solution: 𝑞𝑟𝑥𝑛 = −[𝐶𝑐𝑎𝑙 ∆𝑇𝑐𝑎𝑙 + 𝑚𝐻𝐶𝑙 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇𝐻𝐶𝑙 + 𝑚𝑁𝑎𝑂𝐻 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇𝑁𝑎𝑂𝐻 𝑞𝑟𝑥𝑛 = − [(35.36 𝐽 4.18 𝐽 4.18 𝐽 ) (17℃) + (50.86𝑔) ( ) (−18℃) + (51.49𝑔) ( ) (−18℃)] ℃ 𝑔℃ 𝑔℃ 𝑞𝑟𝑥𝑛 = −[(601.12 𝐽) + (−3826.7064 𝐽) + (−3874.1076 𝐽)] 𝑞𝑟𝑥𝑛 = −[−7099.694 𝐽] 𝑞𝑟𝑥𝑛 = 7099.694 𝐽 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 𝑚𝑁𝑎𝑂𝐻 × 1𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝑁𝑎𝑂𝐻 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 51.49𝑔 × 1 𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝑁𝑎𝑂𝐻 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 0.15447 𝑚𝑜𝑙 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 𝑚𝐻𝐶𝑙 × 1𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝐻𝐶𝑙 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 50.86𝑔 × 1 𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝐻𝐶𝑙 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 0.15258 𝑚𝑜𝑙 Limiting Reactant = 0.15258 mol of HCl ∆𝐻𝑟𝑥𝑛 = 𝑞𝑟𝑥𝑛 𝑚𝑜𝑙𝑒𝑠𝑙𝑖𝑚𝑖𝑡𝑖𝑛𝑔𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡 1 𝑘𝐽 ∆𝐻𝑟𝑥𝑛 = 7099.694 𝐽 × 1000 𝐽 0.15258 𝑚𝑜𝑙 Page 17 Lyceum of the Philippines University - Laguna International School ∆𝐻𝑟𝑥𝑛 = 46.53 𝑘𝐽 % Error H theoretical H exp erimental H theoretical 𝑘𝐽 %𝐸𝑟𝑟𝑜𝑟 = | −55.8 𝑚𝑜𝑙 − −55.8 100% 46.53𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 | × 100% 𝑚𝑜𝑙 %𝐸𝑟𝑟𝑜𝑟 = 1.83% The process or reaction is exothermic. The process for part C is exothermic because the heat inside the calorimeter was released as it is measured by the thermometer. As we all know that if the heat was released then it is an exothermic process. In our experiment, the heat was released as the temperature goes up in the thermometer. As the heat given off in an exothermic process will be the same amount of heat gained by the calorimeter. Same as in our experiment, as time goes on, the temperature stays the same. All measurements have some degree of uncertainty that may come from a variety of sources. When we make a measurement, we generally assume that some exact or true value exists based on how we define what is being measured. While we may never know this true value exactly, we attempt to find this ideal quantity to the best of our ability with the time and resources available. Therefore, all experimental results are wrong. As we do the experiment, during the calibration of calorimeter, the calorimeter must be closed immediately upon mixing the solution to the water inside it. This is part can be considered as a source of error especially if the calorimeter is not immediately closed. When this Page 18 Lyceum of the Philippines University - Laguna Page International School 19 happen, some heat may have lost to the air, making the heat gained by the calorimeter and the water lower than the ideal. This may lead to a wrong record of temperature. Also, the synchronization between starting the time to record data and closing the calorimeter can also cause error. Ideally, temperature recording must start immediately after mixing the sample in the calorimeter, then closing it. But in reality, this procedure is very difficult to do perfectly. The process or reaction is endothermic. As seen in the computation above, the computed value of the enthalpy of the of the reaction is 50.10 kJ. This positive value of the enthalpy of the solution means that the solution absorbed heat. In experiments, errors were unavoidable. The possible sources of error were human error, improper calibrations, measurement estimation, andmeasurement device limitations. These sources may lead to an inaccurate value from what is expected in the report. SUMMARY AND CONCLUSION The conclusion of this experiment is; materials really affect the experiment. On our experiment, we did some mistakes like; didn’t close the cup properly and left a small hole (on the top of the cup where we put the thermometer) and let some heat released. The use of Styrofoam also affects the experiment. If we use other material like beaker, which takes less energy to lose heat (lets the heat escape easier). The heat on the glass beaker Lyceum of the Philippines University - Laguna International School will flow from the water, through the glass, and to our hand. Using paper cup is also not recommended, because it conducts heat. It will affect the calculation and will give us different value. To have the best accurate result, we have to make sure that all the materials are in the best condition. Make sure we have sealed the hole accurately so there’s no way heat will escape. Just in case, cover the Styrofoam cup with another cup for safe in case it’s leaking or spilled If you’re going to have an experiment like this make sure that the cover is unlit so the heat cannot get out and to measure the exact temperature in order to have a successful experiment. For future researchers, mistakes may occur when heat escapes from the cup. Some of the heat was absorbed by the water and the cup, and some heat escaped when we didn't closed the cup in the proper way; We accidentally left the hole that we made to put the thermometer loose and opened, as a result, the heat escaped. This experimental mistake is commonly caused by incorrect measurements of the chemicals which results to wrong outcome. The difference between the measurements of the chemicals or mixtures will result to the wrong measurements between heat capacities after all the calculations were made. Make sure there will no heat will escape from the cup or else, it will come out wrong and failed Page 20 Lyceum of the Philippines University - Laguna Page International School 1 LITERATURE CITED Brooks-Cole, (2003) Adapted from Hall, J.F. Experimental Chemistry, 6th Ed.; Houghton-Mifflin: New York, 2003 McGraw-Hill:Boston, (2007) Standard and Microscale Experiments in General Chemistry, 5th Ed Adapted from Bishop, Bishop, and Whitten Standard and Microscale Experiments in General Chemistry, 5th Ed. p 187. Silberberg, M.S. n.d. Principles of General Chemistry APPENDICES Part A: Determination of the Calorimeter Constant Empty calorimeter Calorimeter + cold water Calorimeter + cold water + hot water Mass (in g) 25.32g 74.92g 121.92g Lyceum of the Philippines University - Laguna Page International School Total mass of water in the calorimeter 2 46.6g Initial 26 °C 64 °C Temperature (cold water) Temperature (warm water) Final 43°C Part B: Heat of Solution Mass (in grams) Calcium chloride 25.32g 74.92g 49.6g 5.00g Empty calorimeter Calorimeter + cold water Cold water Sample solid used urea 25.32g 74.92g 49.6g 5.01g Temperature °C Initial (water only) 26℃ 26℃ Final (solution) 35℃ 24℃ T 9℃ -2℃ Part C: Data and Observations Time After Mixing (sec) Temperature After Mixing (℃) 15 40℃ 30 43℃ 45 43℃ 60 43℃ 75 43℃ 90 43℃ 105 43℃ 120 43℃ 135 43℃ Lyceum of the Philippines University - Laguna Page International School 150 2 43℃ Time After Mixing (sec) Temperature After Mixing (℃) 165 43℃ 180 43℃ 195 43℃ 210 43℃ 225 43℃ 240 43℃ 255 43℃ 270 43℃ 285 43℃ 300 43℃ Lyceum of the Philippines University - Laguna International School Computations Part A: Determination of Calorimeter Constant Given: ∆𝑇𝑐𝑎𝑙 = 17℃ 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 − 𝑚𝑒𝑚𝑝𝑡𝑦 𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 = 74.92𝑔 − 25.32𝑔 𝑚𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 = 49.6𝑔 ∆𝑇𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 = 17℃ 𝑚ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟+ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 − 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 𝑚ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 = 121.92𝑔 − 74.92𝑔 𝑚ℎ𝑜𝑡𝑤𝑎𝑡𝑒𝑟 = 47𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 ∆𝑇ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 = −21℃ 𝑔℃ Solution: Ccal ΔTcal mcold cwater ΔTcold water mhotcwater ΔThot water 0 4.18 𝐽 4.18𝐽 𝐶𝑐𝑎𝑙 (17℃) + (49.6𝑔) ( ) (17℃) + (47𝑔) ( ) (−21℃) = 0 𝑔℃ 𝑔℃ 𝐶𝑐𝑎𝑙 (17℃) + (3524.576𝐽) + (−4125.66𝐽) = 0 𝐶𝑐𝑎𝑙 (17℃) − 601.084𝐽 = 0 𝐶𝑐𝑎𝑙 (17℃) 601.084𝐽 = 17℃ 17℃ Page 1 Lyceum of the Philippines University - Laguna International School 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ The Calorimeter constant is equal to 35.36 J/°C Part B: Heat of Solution Given: 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 + 𝑚𝐶𝑎𝐶𝑙2 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 49.6𝑔 + 5.00𝑔 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 54.6𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑎𝑙𝑢𝑒 = − 82.8 𝑘𝐽/𝑚𝑜𝑙 ∆𝑇 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ∆𝑇 = 26℃ − 36℃ ∆𝑇 = −10℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Solution: ∆𝐻𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑜𝑓 𝐶𝑎𝐶𝑙2 𝑞𝑟𝑥𝑛 = −[𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇) + 𝐶𝑐𝑎𝑙 ∆𝑇] 4.18 𝐽 𝐽 𝑞𝑟𝑥𝑛 = −[(54.6𝑔) ( ) (−10℃) + (35.36 )(−10°𝐶) 𝑔℃ °𝐶 𝑞𝑟𝑥𝑛 = −[(−2282.28 𝐽) + (−353.6 𝐽)] Page 2 Lyceum of the Philippines University - Laguna International School 𝑞𝑟𝑥𝑛 = −[−2635.88 𝐽] 𝑞𝑟𝑥𝑛 = 2635.88 𝐽 2635.88𝐽 × ∆𝐻𝐶𝑎𝐶𝑙2 = 1 𝑘𝐽 1000𝐽 0.0451𝑚𝑜𝑙 ∆𝐻𝐶𝑎𝐶𝑙2 = 58.45 𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 %𝐸𝑟𝑟𝑜𝑟 = | 𝑘𝐽 −82.8 𝑚𝑜𝑙 − 58.45 𝑚𝑜𝑙 𝑘𝐽 −82.8 𝑚𝑜𝑙 | × 100% %𝐸𝑟𝑟𝑜𝑟 = 1.71% Given: 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑚𝑐𝑜𝑙𝑑𝑤𝑎𝑡𝑒𝑟 + 𝑚𝑢𝑟𝑒𝑎 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 49.6𝑔 + 5.01𝑔 𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 54.61𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑎𝑙𝑢𝑒 = 14.0 ∆𝑇 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ∆𝑇 = 26℃ − 24℃ 𝑘𝐽 𝑚𝑜𝑙 Page 3 Lyceum of the Philippines University - Laguna International School ∆𝑇 = 2℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Solution: ∆𝐻𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑜𝑓 𝑈𝑟𝑒𝑎 (𝐶𝐻4 𝑁2 𝑂) 𝑞𝑟𝑥𝑛 = −[𝑚𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇) + 𝐶𝑐𝑎𝑙 ∆𝑇] 𝑞𝑟𝑥𝑛 = −[(54.61𝑔) ( 4.18 𝐽 𝐽 ) (2℃) + (35.36 )(2℃) 𝑔℃ ℃ 𝑞𝑟𝑥𝑛 = −[(456.5396 𝐽) + (70.72 𝐽)] 𝑞𝑟𝑥𝑛 = −[527.2596 𝐽] 𝑞𝑟𝑥𝑛 = −527.2596 𝐽 1 𝑘𝐽 ∆𝐻𝑢𝑟𝑒𝑎 = (−527.2596 𝐽) × 1000 𝐽 0.0834 𝑚𝑜𝑙 ∆𝐻𝑢𝑟𝑒𝑎 = −6.32 𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 𝑘𝐽 %𝐸𝑟𝑟𝑜𝑟 = | 14.0 𝑚𝑜𝑙 − (−6.32 𝑚𝑜𝑙) 𝑘𝐽 14.0 𝑚𝑜𝑙 %𝐸𝑟𝑟𝑜𝑟 = 1.45% | × 100 Page 4 Lyceum of the Philippines University - Laguna International School Part C: Heat of Neutralization Given: 𝑚𝐻𝐶𝑙 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+(𝑁𝑎𝑂𝐻+𝐻𝐶𝑙) − 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑁𝑎𝑂𝐻 𝑚𝐻𝐶𝑙 = 127.67𝑔 − 76.81𝑔 𝑚𝐻𝐶𝑙 = 50.86 𝑔 𝑐𝑤𝑎𝑡𝑒𝑟 = 4.18 𝐽 𝑔℃ 𝑚𝑁𝑎𝑂𝐻 = 𝑚𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟+𝑁𝑎𝑂𝐻 − 𝑚𝑒𝑚𝑝𝑡𝑦 𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑚𝑁𝑎𝑂𝐻 = 76.81𝑔 − 25.32𝑔 𝑚𝑁𝑎𝑂𝐻 = 51.49𝑔 ∆𝑇𝐻𝐶𝑙 = 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑇𝑓𝑖𝑛𝑎𝑙 ∆𝑇𝐻𝐶𝑙 = 25℃ − 43℃ ∆𝑇𝐻𝐶𝑙 = −18℃ ∆𝑇𝑁𝑎𝑂𝐻 = 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑇𝑓𝑖𝑛𝑎𝑙 ∆𝑇𝑁𝑎𝑂𝐻 = 25℃ − 43℃ ∆𝑇𝑁𝑎𝑂𝐻 = −18℃ 𝐶𝑐𝑎𝑙 = 35.36 𝐽/℃ Theoretical Value: ∆𝐻𝑟𝑥𝑛 = −55.8 𝑘𝐽 𝑚𝑜𝑙 Page 5 Lyceum of the Philippines University - Laguna International School Solution: 𝑞𝑟𝑥𝑛 = −[𝐶𝑐𝑎𝑙 ∆𝑇𝑐𝑎𝑙 + 𝑚𝐻𝐶𝑙 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇𝐻𝐶𝑙 + 𝑚𝑁𝑎𝑂𝐻 𝑐𝑤𝑎𝑡𝑒𝑟 ∆𝑇𝑁𝑎𝑂𝐻 𝑞𝑟𝑥𝑛 = − [(35.36 𝐽 4.18 𝐽 4.18 𝐽 ) (17℃) + (50.86𝑔) ( ) (−18℃) + (51.49𝑔) ( ) (−18℃)] ℃ 𝑔℃ 𝑔℃ 𝑞𝑟𝑥𝑛 = −[(601.12 𝐽) + (−3826.7064 𝐽) + (−3874.1076 𝐽)] 𝑞𝑟𝑥𝑛 = −[−7099.694 𝐽] 𝑞𝑟𝑥𝑛 = 7099.694 𝐽 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 𝑚𝑁𝑎𝑂𝐻 × 1𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝑁𝑎𝑂𝐻 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 51.49𝑔 × 1 𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝑁𝑎𝑂𝐻 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝑁𝑎𝑂𝐻 𝑢𝑠𝑒𝑑 = 0.15447 𝑚𝑜𝑙 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 𝑚𝐻𝐶𝑙 × 1𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝐻𝐶𝑙 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 50.86𝑔 × 1 𝑚𝐿 1𝐿 3.0 𝑚𝑜𝑙 × × 1𝑔 𝐻𝐶𝑙 1000𝑚𝐿 1𝐿 𝑚𝑜𝑙𝐻𝐶𝑙 𝑢𝑠𝑒𝑑 = 0.15258 𝑚𝑜𝑙 Limiting Reactant = 0.15258 mol of HCl ∆𝐻𝑟𝑥𝑛 = 𝑞𝑟𝑥𝑛 𝑚𝑜𝑙𝑒𝑠𝑙𝑖𝑚𝑖𝑡𝑖𝑛𝑔𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡 1 𝑘𝐽 ∆𝐻𝑟𝑥𝑛 = 7099.694 𝐽 × 1000 𝐽 0.15258 𝑚𝑜𝑙 ∆𝐻𝑟𝑥𝑛 = 46.53 𝑘𝐽 Page 6 Lyceum of the Philippines University - Laguna International School % Error H theoretical H exp erimental H theoretical 𝑘𝐽 %𝐸𝑟𝑟𝑜𝑟 = | −55.8 𝑚𝑜𝑙 − 100% 46.53𝑘𝐽 𝑚𝑜𝑙 𝑘𝐽 −55.8 𝑚𝑜𝑙 | × 100% %𝐸𝑟𝑟𝑜𝑟 = 1.83% Figure 1. Coffee cup calorimeter without the thermometer Figure 2. Measuring of 50.0 mL of distilled water using the graduated cylinder Page 7 Lyceum of the Philippines University - Laguna International School Figure 3. Measuring distilled water with NaOH Page 8 Lyceum of the Philippines University - Laguna Page International School 9 CONTRIBUTION TO THE SCIENTIFIC PAPER Member Contribution Del Valle, Alyssa L. Materials and Methods Manuel, Robin Piolo M. Recommendation Motas, Hannah Faye A. Results and Discussion Pagaduan, Mark Gerald N. Abstarct and Introduction Ricablanca, Princess Jane D. Santos, Claude Jayson U. Results and Discussion; Abstract Introduction Seleteria, Richel B. Materials and Methods Torres, Khim Harold Summary and Conclusion . Signature