After the calorimeter constant is found we can move on to part two of the experiment, where we will test each of the four salts in the calorimeter to find out if the salt will be used for a hot or cold pack. Our goal is to first determine the q_dissolution and then to find the heat of dissolution. A -〖∆H〗_dissolution will be an exothermic reaction which indicates that the salt would go in a hot pack. While a 〖∆H〗_dissolution will be an endothermic which indicates that the salt would go in an ice pack.
Calculations for determining the 〖ΔH〗_(dissolution ) of each salt
Csolution = specific heat of water = 4.184 J/g°C
ΔHdissolution=qdissolution/(moles of substance dissolved)
q_dissolution = the opposite of the answer you get for- q_dissolution.
*For where M is the mass of the solution, C is the thermal Constant of water: 4.184 J/g°C, ∆T is the change in Co , Q is the energy of dissolution.
In order to determine the mass of salt required for the ice pack to reach 0.0°C and hot pack to reach 65°C, we must set the ΔHdissolution which will be calculated from our trial equal to the ΔHdissolution of hot/cold pack containing 100 mL of water and reaching a temperature of 65°C/0.0°C. This equation is given below:
(Cdissolution ×M dissolution × ΔT dissolution)/(moles of substance dissolved)=(Cdissolution(x+100g water)dissolution ΔTdissolution x g of substance dissolved )/█(g/mol of substance dissolved@)
*The left side of the equation will represent the data from the experiment, and the right side represents our hypothetical calculations. By plugging in either 65°C or 0°C (depending on if were solving for the hot or cold pack), and then solving for the x value, we can calculate the mass needed to raise or lower the pack to the specified temperature.
CAUTION: Students must wear departmentally approved eye protection while performing this experiment. Wash your hands before touching your eyes and after completing the experiment.
WARNING: Lithium chloride, Calcium chloride, Ammonium nitrate, and Potassium chloride our hazardous and can cause irritation with skin and eye contact. Areas should be flushed with cool water immediately after exposure.
PART A: Setting Up the MeasureNet station
Press the On/Off button to turn on the MeasureNet workstation.
Press Main Menu, the press F2, Temperature, next press F1, Temperature vs. Time.
Half fill a 150-mL beaker with ice and water. Press Calibrate to calibrate the temperature probe. When prompted, enter 0.0°C as the actual temperature of the constant temperature bath (ice water). Press Enter. Insert the temperature probe in the ice water. Swirl the temperature probe until the temperature approaches and stabilizes near 0°C (it may not read exactly 0°C). Press Enter.
Remove the temperature probe from the ice water bath.
Press Set Up to establish scan parameters for the...