Experiment 25 Pre Laboratory Assignment Calorimetry Pogil

Abstract: This experiment was done to discover more about heat transfer in regards to the law of conservation of energy. 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 identity of an unknown metal using its unique property of specific heat. We did this by following a simple procedure of heating up a metal and then transferring it into a Styrofoam cup containing water at room temperature. By observing and recording the temperature changes in both the water and the metal we were able to determine the specific heat and molar mass of the unknown metal. Nonetheless, the specific heat of the unknown metal (#3) resulted to be 0.4300J/g ° C with an estimated molar mass of 58.1, identifying the unknown metal as Co. Part 2 allowed us to calculate ∆H neutralization that occurred in when a strong acid and a strong base were mixed. Once again with the use of Styrofoam cups were able to measure change in temperature inside the Styrofoam cup once the acid and base reacted. The heat of neutralization resulted to be the following: the heat neutralization for HCl when mixed with NaOH is 54.1kJ/molH 2 O. The heat neutralization for HNO 3 with NaOH is 55.7kJ/molH 2 O. Lastly, this experiment allowed us to determine and the ∆H of a solution upon the dissolution of salt. When salt dissolves in water it can have a ∆H that is lattice (endothermic) or a ∆H that is hydration (exothermic) with an average heat of solution of 20370J/mol of KBr.The ∆H for this reaction is calculated to be lattice. The temperature of the water in the calorimeter dropped thus making it an exothermic reaction. In Part A of the experiment we recorded the mass of the metal and water along with the change in temperature of both. Knowing this information along with the specific heat of water we were able to solve for the heat evolved( q ) in water with the equation. We then referred to q water = - q metal  ( ms∆T= - ms∆T )and used the heat evolved by water to solve for the specific heat of the metal. We manipulate the same equation into and which allows us to calculate of our unknown metal. Based on our Introduction: The main purpose for performing this experiment was to determine the specific heat of an unknown metal, the name of the metal, the enthalpy of neutralization of two different reactions that consisted of a strong acid and a strong base, and the whether the ∆H when salt dissolved in water was lattice or hydration reaction. We did this by using known information such as the masses, specific heat of water, change in temperature (based on final and initial temperature), and number of moles that reacted. In this experiment both my acid and base started at 21.2 ° C. Based on the graph the masximum temperature that occurred in the reaction is 27.8.

As stated in the Law of Conservation of Energy, “energy can neither be created nor destroyed”. With all chemical and physical changes, there is a transfer of energy (heat). Calorimetry refers to the process of measuring the amount of heat released or absorbed during a chemical reaction. The heat change in change in chemical reactions is quantitatively expressed as the enthalpy (or heat) of reaction ∆ H, at constant pressure. By knowing the direction of heat Fow, one can determine whether or not a reaction is exothermic, which refers to releasing heat, or endothermic, meaning to absorb heat. Calorimetry plays a huge role in everyday life including maintaining body temperatures and metabolic processes in humans. A calorimeter is a laboratory apparatus that is used to measure the quantity and direction of heat Fow accompanying a chemical or physical change. There are di±erent types of calorimeters which vary according to the kind of reaction and precision desired. In this particular experiment, a constant- pressure calorimeter was used. This type of calorimeter measures the change in enthalpy of a reaction occurring in a solution, in which the atmospheric pressure is remaining constant. The calorimeter apparatus utilized consisted of two nested Styrofoam cups with a cardboard lid and a small hole, allowing for the insertion of the thermal probe to measure the temperature changes and patterns throughout the experiment. The ²rst part of this experiment (Part B) focused on determining the enthalpy of neutralization for a strong acid-strong base reaction. The enthalpies of various neutralization reactions will be found, including reactions between strong electrolytes (NaOH with HCl and NaOH with HNO3). In this section, the ∆ H of neutralization will be determined by utilizing the Styrofoam cups to measure the change in temperature inside the Styrofoam cups once the acid and base reacted. The results in this part of the experiment can be used to determine whether this neutralization reaction between a 2


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