THE CALIBRATION OF THE CALORIMETER ANDTHE HEAT OF NEUTRALIZATION Submitted by: Arnel S. Ardemer Submitted to: Prof. Gloria Jesusa D. Baltazar Chemistry 72 (Laboratory) 18 March 2013 and they remain “indispensable” not only in academic and industrial labs. Ardemer I. or to say. on predicting . electrical. when a certain reaction occurs. Every chemical change is accompanied by change in chemical energy. The concept behind the fact that there are ways how to measure the quantity of heat being released in a certain reaction. Modern atomic theory allows everyone to consider other forms of energy – solar. especially in the industries. In everything that exists consist of energy that is somewhat hidden until they are observed especially when an object undergoes a certain change. mostly observed in a form of heat. Moreover. but in the home as well. the energy content of the matter also changes 1. and chemical – as examples of potential and kinetic energy on the atomic and molecular scales. the atoms are materials that served as “banks of energy”. each cancels the properties of the other in a process called neutralization1. No matter what the details of the situation. Neutralization mainly involves the production of water. Introduction Matter and its basic component. And it was also observed that when an acid and a base are mixed. heat released by the system at a constant given pressure made a great contribution in estimation. the effect could be visibly observed by changes in heat energy. Whenever matter changes. nuclear. a quantity of heat is produced. whether chemically or physically. it was known that when acids and bases react.THE CALIBRATION OF THE CALORIMETER AND THE HEAT OF NEUTRALIZATION Arnel S. Acids and bases have been used as laboratory time of the alchemists. the amount of heat to be released or absorbed by a particular reaction (whether would it be endothermic or exothermic. (4) to distinguish the enthalpy of neutralization when a weak acid or a strong acid is used. using the direct calorimetry method on which the reaction is to be ensured to occur to completion without side reactions. if the latter is so. the experiment was done with the following objectives: (1) to measure the heat of neutralization of a particular neutralization reaction. and (5) to calibrate a simple calorimeter. the overall significance is to verify the amount of heat released as a neutralization process occurs to form a mole of water and appreciate its concept in relation with daily life and additional understanding towards the behavior of matter and its changes. developed the thought of thermochemistry – the study of enthalpy changes in chemical processes 2. The experiment mainly focused on the heat of neutralization of acids and bases. especially its effect in the environment). . particularly NaOH as the base and HCl and CH 3COOH as the acids used. then would the heat released be a great thing to take deal with. Thus. (3) to determine the enthalpy change undergone by the neutralization of acid and base to form a certain amount of water. (2) to appreciate the concept behind the exothermic nature of neutralization reaction. In this experiment. The experiment was made to have the investigation. The specific heat (c) of a substance is the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius. The heat capacity (C) of a substance is the amount of heat required to raise the temperature of a given quantity of the substance by one degree Celsius. Direct calorimetry is the method on which one could measure especially at constant pressure. but in the Arrhenius sense. which could be measured quantitatively. It has the units J/g·C°. A calorimeter is a closed container designed specifically for measurement of heat changes on a chemical system 4. The meaning of acid-base reactions has changed along with the definitions of acid and base. When an acid and a base react. Its unit is J/°C. Chemically speaking. The key towards understanding the concepts of calorimetry depends in the appreciation on specific heat and heat capacity.ion from the base combine to form H2O1.II. Theoretical Background Acids and bases have their nature in common. A calorimeter is a device being used for centuries up to the present in determining the heat being released or absorbed by a particular reaction. As the definition goes. neutralization occurs when the H+ ion from the acid and the OH. respectively thermodynamically produce a certain amount of heat which produced upon the combination of the two to form water. water. the combination of H + and the OH— species in the dissociated acids and bases. . they undergo neutralization. the Arrhenius definition of acids and bases fits this nature on which when they are mixed produces its common product. the enthalpy of neutralization of a particular acid and base reaction. when heat capacity is known together with the change of temperature. These factors served very important towards understanding the nature of heat of neutralization. Heat changes in the neutralization reaction vary mainly on the strength of the acids used.Specific heat is an intensive property whereas heat capacity is an extensive property. Arrhenius suggested that the heat of reaction was always the same because the actual reaction was always the same – a hydrogen ion and a hydroxide ion formed water: .2 kJ per mole of water formed. Earlier studies observed that all neutralization reactions between strong acids and strong bases (those that dissociate completely in water) had the same heat of reaction. its specific heat and the change of temperature it undergone. No matter which strong acid and base reacted. Heat (q) could be measured in terms of determining the mass of the object. the amount of heat could be measured. But conventions suggest the utilization of the unit Joule in dealing with heat. or to say. Since the pressure in constant. and no matter which salt formed. Hº was about -56. q = mcT where m= mass of the object c = specific heat of the object T = change in temperature (Tf – Ti) equation 1 q= CT where C= heat capacity of the certain mass of the object T = change in temperature (Tf – Ti) equation 2 The unit of heat is either in calories or in Joules. with the sense of heat capacity. The experiment used a constant pressure calorimeter which is simpler compared to constant volume calorimeter. thus the heat changes being measured would be equal to the enthalpy changes (q. The equations for these definitions are shown by equations 1 and 2. III. A lid cover was made of polystyrene board.0 M CH3COOH. thermometer holder. The experiment was started by making a simple calorimeter out of polystyrene cups. alcohol lamp. wire gauze. pipette and aspirator.0 M HCl. materials and reagents: apparatuses involved the thermometer. the heat of reaction is lower than in equation 3 this is because weak acids and bases do not dissociate fully on water. Materials involved are: polystyrene (styrofoam) cup (2 pieces) polystyrene board (for calorimeter lid). and distilled water. plastic ring. Two polystyrene cups were fused together to form a one double layered cup that is intended to maximize the insulation and isolation of heat.in the solution. On the other hand.0 M NaOH. iron stand. not giving its overall H+ and/or OH. iron ring.2 kJ/mol equation 3 Thus for any reaction that involves the presence of strong acids and bases would yield the same heat of reaction. Methodology The experiment was performed using the following apparatuses. 1. volumetric flask. and graduated cylinder. wooden stick. and cutter. A circular canal was made on the board in order for the mouth of the cup . when a weak acid or a weak base is involved. 1. Chemicals involved 1.H+(aq) + OH-(aq) H2O(l) rHº = -56. Thus only fewer of these species react to form water. 500 mL each 1. As the heat capacity was already obtained.0 M of CH 3COOH was prepared. the heat capacity of the calorimeter. the same with the room temperature was placed in the calorimeter. the experiment was performed.0 M of HCl and 1.0 M of NaOH. Before the heat of neutralization experiment was performed. to determine its heat capacity. First done was the neutralization between HCl and NaOH. Fifty milliliters of NaOH was placed on the clean dry calorimeter. the constructed simple calorimeter was calibrated first. pipette and aspirator and distilled water. Using the volumetric flask. with the temperature of 28°C. Fifty milliliters of water.1 M HCl was poured into the calorimeter and the calorimeter was covered and stirred with the built-in stirrer and the temperature was obtained every 15 seconds for three minutes. After few minutes. Noting that all the chemicals must have equal temperature ( in thermal equilibrium) with the surroundings. . a weak acid and the procedures were followed as it was in the HCl-NaOH neutralization. Another setup was performed. These chemicals where then used for the experiment. Calibration was done for three trials and taken its mean as the heat capacity of the calorimeter. The temperature of the mixture was then obtained and was recorded. noting the temperature of the mixture every 15 seconds for 3 minutes. the temperature was measured and served as the initial temperature. 1.to fit in. Another 50 mL of water was heated up to 56°C. The temperatures were recorded and were used to calculate the C cal. A 50 mL of the prepared 0. But the difference was that the HCL was replaced with acetic acid. the heat of neutralization was performed. Two holes were made on the board intended for the thermometer and the other for the wooden stirrer made of wood and plastic ring. Both temperatures were noted and the hot water was poured into the calorimeter. Table 1: the Calibration of the Calorimeter TRIAL 1 TRIAL 2 TRIAL 3 Vcold water Vhot water mcold water mhot water 50 mL 50 mL 50 g 50 g 50 mL 50 mL 50 g 50 g 50 mL 50 mL 50 g 50 g Tcold water (Tc) 28 ºC 28 ºC 28 ºC Thot water (TH) 56 ºC 56 ºC 56 ºC Time (s) Tmixture (TM) Tmixture (TM) Tmixture (TM) 15 30 45 60 75 90 105 120 135 150 165 180 ºC 40 40 40 40 40 40 40 40 40 40 40 40 16 Cº ºC 40 40 40 40 40 40 40 40 40 40 40 40 16Cº ºC 41 41 41 41 41 41 41 41 41 41 41 41 15Cº Calculated Ccal = 15. room temperature. the volume and the various temperatures of water being used and the 180 second tally was the monitor of the temperature of 3 minutes.IV. The T was then measured form the maximum temperature minus the initial. The mass of . In the calibration of the calorimeter.28 cal/ C Table 1 showed the mass. Results The experiment on heat of neutralization gathered the following results. the results were presented on table 1. The reaction had a change in temperature of 6C° and arrived using respective calculation to the calculated heat of neutralization to be – 57. the heat of neutralization between the reaction of sodium hydroxide and acetic acid is shown on table 3.8 kJ/mol. all liquid solutions were assumed to have density of 1g/mL.water was assumed to be the same as its volume. the heat of neutralization setup was performed. Table 3: heat of neutralization (NaOH-CH3COOH) .5 % In the experiment. On the other setup. And the results are shown in table 2: Table 2: heat of neutralization (NaOH-HCl reaction) Room temp VNaOH VHCl TNaOH THCl 28ºC 50 mL 50 mL 28ºC 28ºC Time (s) 15 30 45 60 75 90 105 120 135 150 165 180 T Calculated heat of TM (ºC) 34 34 34 34 34 34 34 34 34 34 34 34 6 -57.8 kJ/mol neutralization % error 4. table 2 showed the result of the experiment in the heat of neutralization of NaOH and HCl reaction. Using the calculated heat capacity of the calorimeter. assuming that the density is 1g/mL. These concepts led to the objective of this experiment to experimentally .8 kJ/mol netralization % error 4. Thus upon formation water in the neutralization. Discussion The basic principle that governs the experiment is the conservation of energy on which the heat lost by the system will always be equal to the heat gained by the surrounding or another system. heat is also released. Another one is that the neutralization of an acid and a base produces water and its side product as heat.5 % The procedures on the earlier neutralization reaction setup were followed on the latter. acetic acid. only that the acid used is a weak acid.Room temp VNaOH V CH3COOH TNaOH T CH3COOH 28ºC 50 mL 50 mL 28ºC 28ºC Time (s) 15 30 45 60 75 90 105 120 135 150 165 180 T Calculated heat of TM (ºC) 34 34 34 34 34 34 34 34 34 34 34 34 6 -57. V. Provided with the concept that energy is conserved. to determine its heat capacity. It was in here that one should determine how much heat could be absorbed by the calorimeter. The calibration of the simple calorimeter was the initial step done towards measuring the heat of neutralization of a particular reaction.measure the heat of neutralization of a particular neutralization reaction and compare it to the theoretical values established by the literatures. that is. a formula derived (equation 4) was used for the calibration of the calorimeter. . It is expected that the calorimeter would absorb an amount of heat so it must be determined so that the heat it absorbed would be added to the calculation of the overall heat involved in the reaction. .Using the derived equation and the data gathered during the experiment. the heat capacity of the calorimeter was measured. A sample calculation is shown on illustration 1. 0 M) and the strong acid used was HCl (1. Taking the mean of the three trials. The weak acid used on the second setup was CH3COOH (1. The mean heat capacity of the calorimeter was the one used in the succeeding experiment on heat of neutralization. The strong base used was NaOH (1.28 cal/C°. that is the amount of heat released when an acid and a . Trial 1 and 2 have 16.0 M).67 cal/Cº and trial 3 has 15. The experiment started with the heat of neutralization of NaOH-HCl neutralization reaction.0 M). The calculations shown in illustration 1 are the calculations for trial 1 and 2.20 cal/C°. Trial 3 was calculated on the same manner. The heat of neutralization experiment was performed using a pair of a strong acid and a strong base and the other one was a pair of weak acid and a strong base. the average heat capacity of the calorimeter was found to be 15. The results presented in table 2 showed the information needed to experimentally determine and calculate the heat of neutralization of the particular exothermic reaction.Illustration 1: the calculation of trials 1 and 2. llustration 2: calculation of the heat of neutralization of HCl-NaOH reaction Illustration 2 showed the calculated HCl-NaOH heat of neutralization to be –57.05 moles and obtained the enthalpy of reaction per mole of water formed. Thus the heat calculated was divided with 0.2 kJ/mol 3. In the literatures. Illustration 2 showed the calculation for determining the heat of neutralization of the acid-base reaction. acetic acid instead of hydrochloric acid was performed using the same procedure and the heat of neutralization . the amount of water produced in the reaction of 50 mL each of HCl and NaOH is found to be 0.5% error. Thus the experiment had 4.base reacts to form water. On the other setup where the acid used was a weak acid.05 moles.8 kJ/mol. the theoretical value of this neutralization is found to be –56. Stoichiometrically determined. General errors in the experiment could be traced as mistakes in thermometer readings due to the poor precision of the thermometer used (±1). This may be the result of error in preparation of the solutions. The prepared solutions might also be the factors.43 kJ/mol 4. They were not standardized. The value of the calculated heat capacity of the calorimeter might be higher than the actual that in return. This might be because the amount of acids and bases are higher that they produced greater amount of heat. Some of the errors of the experiment were too visible and could be traced in many ways. Conclusion and Recommendation . Thus the error of the experiment was found to be 4. The experiment’s calculated heat of neutralization based on the data on table 3 was –57.4%. thus if there would be higher amount of acids and base present in the substance than the recorded concentration would give larger amount of heat produced. would give a higher value of heat of neutralization. First to consider was the heat of neutralization of acetic acid should be lesser than that of the HCl-NaOH reaction due to the fact that weak acids tend not to dissociate fully in water and thus fewer H+ ions would react to form water.8 kJ/mol.was calculated using the same process as shown in illustration 2. Literature mentioned the heat of neutralization of acetic acid – sodium hydroxide reaction to be –55. VI. The experimental measurement of the heat of neutralization with lesser errors in the experiment gave way to appreciate that there really is a certain quantity of heat being produced in the neutralization reactions. LAIDLER. The enthalpy differences between strong acidstrong base and weak acid-weak base reactions were not that appreciated because of some certain errors but the concept behind them were well understood. CHANG. 3. 2. Principles of General Chemistry. Chemistry. USA: McGraw-Hill.J. USA: McGraw-Hill. M. 3rd ed. Chemistry: The Molecular Nature of Matter and Change. SILBERBERG. 10th ed. (2013). VII. M. 3rd ed. New York. SILBERBERG. United States of America: Houghton Mifflin Co.H. MEISER. Physical Chemistry. USA: McGraw-Hill. References 1. . K. 2007. New York. and J. As the experiment is to be performed for the next time. 4th ed.The experiment on the determination of heat of neutralization on two setups of acid base reactions were the important tools towards the higher appreciation and understanding of the concepts of enthalpy changes in the systems as they would undergo some certain reactions.1999. New York. R. it is recommended that the standardization of the solutions to be used is done and the thermometer to be used must be as precise as possible. 2006. The calorimeter might be improved by using an ultra thick polystyrene cup to ensure that there should be no heat lost to the environment. 4.