a In other cases it is the component that is in a smaller amount 3 The solvent

A in other cases it is the component that is in a

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a. In other cases, it is the component that is in a smaller amount. 3) The solvent is the liquid substance in which the solids or gases are dissolved. a. In other cases, it is the component that is in a larger amount. 4) When a solid dissolves in water, an energy change will always result. a. Heat can be evolved or absorbed when an ionic compound dissolves in water. 5) The dissolving process occurs in two distinct steps: a. The first step is the breaking down of the solid crystal lattice. i. This process is endothermic (absorbing energy). b. The second step is the hydration of the individual particles by the solvent. i. This process is exothermic (releasing energy). 6) If the first step is dominant in the course of dissolving, then the process will be endothermic. 7) If the second step is dominant in the course of dissolving, then the process will be exothermic. 8) The heat of solution (ΔH sol ) can be calculated. a. At constant pressure, the heat exchanged is equal to the heat of solution: i. q p = ΔH sol Procedure for the Molar Heat of Fusion of Water: 1) Place about 400 – 500 mL of deionized water into a 600 mL beaker and place onto a hotplate. a. Heat up the water to between 60 o C and 70 o C. Experiment #8A Barnett
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43 b. Note: If the water is hotter than needed, remove from the hotplate with beaker tongs or hot mitts and then add a quantity of room temperature deionized water. 2) While the water is heating up, obtain the mass of two clean and dried empty Styrofoam cups with a cap. a. These two cups should be stacked on top of one another and the cap should have a hole in it to facilitate the use of your thermometer. b. This set of Styrofoam cups will function as your calorimeter. c. Record mass in data table. 3) Once the water temperature is appropriate, add enough warm water to the pre– weighed set of cups to fill between 50–60% full. a. Make sure that you do not add too much warm water if an analytical balance is used because this large mass may overwhelm the balance. 4) Obtain the mass of the set of cups containing the warm water with the cap on top. a. Ensure that no water is clinging to the outside walls of the Styrofoam cups. Dry with a paper towel if necessary. 5) Measure the temperature of the warm water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1 o C – 0.01 o C). 6) Immediately following this measurement, add one large ice cube*. a. *If smaller ice cubes are used, two to four may be necessary. b. Ensure that none of the warm water is allowed to splash out. 7) Replace the cap and gently swirl the contents of the calorimeter to allow for heat to be properly transferred within. a. Do not allow any of the water to splash out during this process. 8) Once the ice has melted and the temperature has stabilized, record the final temperature of the cool water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1 o C – 0.01
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  • Spring '19
  • Chemistry, Chemical reaction, Timothy Barnett

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