5 pages/≈2750 words
Heat of Reaction and Solution (Lab Report Sample)
The main aim of this experiment was to determine the energy between initial and final states of a solution. In this lab, both exothermic and endothermic processes were illustrated. The lab also aimed at measuring the amount of heat absorbed or dissolved in various reactions. source..
Studentâ€™s Name Professorâ€™s Name Course Date Heat of Reaction and Solution Purpose The main aim of this experiment was to determine the energy between initial and final states of a solution. In this lab, both exothermic and endothermic processes were illustrated. The lab also aimed at measuring the amount of heat absorbed or dissolved in various reactions. Introduction Calorimetry is a technique where the heat effect of a given procedure can be measured, with this procedure being a physical or chemical change such as acid-base neutralization. The instrument used is a calorimeter, which can directly measure temperature, thus determining heat effect. Calorimetry is utilized in thermochemistry for the determination of enthalpy and heat capacity among other properties (David 100). Further, energy measurement is a way to analyze the relationship between the properties of a material and energy structure. Enthalpy, H, is given by the following formula: H= U+PV, Where U is the internal energy, P the pressure, and V is the volume of the system, and H is the heat at a constant pressure. Enthalpy changes are used to directly study thermodynamic effects. In this case, a Styrofoam cup calorimeter (calorimetry with constant pressure) was applied. The relations between an amount measured in this calorimeter and the heat effect produced (heat balance equation) are used to give temperature as a function of generated heat from the calorimeter. In chemical processes, energy differences are mostly observed between the final and initial states due to either heat absorption (endothermic processes) or heat production (exothermic processes) (Hundsdorfer 102). In this experiment, both cases are depicted using the following reactions CITATION Dav10 \l 1033 : 252412551625500HClaq+NaOHaq H2 O+NaClaq(1) 263842543053000HNO3aq+NaOHaq H2 O+NaNO3aq(2) 263842541211500CH3CO2Haq+NaOHaq H2 O+CH3CO2Naaq(3) 252412545021500KNO3s+34H2 Ol KNO334H2 O3(4) Where (aq) indicates a substance in aqueous solution, (l) a liquid, and (s) a solid. Reactions 1-3 are between acids and bases (neutralizations) with acids in equations 1 and 2 being strong and weak in 3. Further, there is enthalpy of solution, also known as heat of solution in reaction 4 since heat is absorbed at constant pressure (Calvet and Henri 54). In an exothermic process where heat is released, the enthalpy H is negative, while in an endothermic one, the enthalpy is positive. The units of H are given as cal/mole of one of the reactants used or a product consumed. The heat of solution H can be given as: qcalorimeter=wsaltcsalttf-ti+wwatercwaterti-t2 With the specific heat and amount of KNO3 being small, the equation can be simplified to: qcalorimeter=wwatercwater(tf-t2) but qreaction= -qcalorimeter so qcalorimeter= -wwatercwater(tf-t2) Heat produced in an exothermic process goes to the water in which the products are dissolved. It is noteworthy that the calorimeter determines the warmth of the water. The amount of heat produced is as a result of a given temperature change and can be solved by applying the heat capacity equation below: Heat change = m C T(units are joules) Where heat is the product of mass(m), specific heat capacity(C), and temperature change(T), The energy between the initial and final states can, thus, be determined. Also, both exothermic and endothermic processes can be illustrated, and the amount of heat produced in the reactions (1-4) can be measured. Safety Precautions Lab coats, goggles, and gloves were used in this lab to ensure safety. Procedure The insulating calorimeter was a Styrofoam cup with a thermometer and stirring rod. 75ml of 2M NaOH was placed in the cup and the temperature was recorded. 75ml of 2M HCl was added and completely stirred with the thermometer. The highest temperature was noted. The same procedure was repeated for reactions 2 and 3. The temperature change was found in order to calculate the heat absorbed. Further, the number of moles of the reacting acid and base were estimated and H/mole obtained for each neutralization reaction. For reaction 4, 150ml of water (50ËšC) was transferred into an 8oz Styrofoam cup. After that, 25g of KNO3 was weighed out with its temperature assu...
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