Q2

Chemical ice packs and hot packs, which are often used to treat injuries, contain certain types of salts. . The Ice pack contains this specific salt, CaCl₂.

Chemical ice/hot packs work by breaking a seal in the packaging that allows the salt to mix with gel (composed primarily of water). Depending on the salt in the pack, the reaction will either be endothermic or exothermic.

a. Determine the molar enthalpy of solution for your assigned salt, if 5.00 g of salt dissolves in 100.0 mL of water. Before the ice/hot pack is activated (i.e. seal broken) it is at room temperature, 22.0 oC. After the ice/hot pack is activated, its temperature is 52^oC.

b. Based on your calculation of the molar enthalpy of solution for your assigned salt, would it be used in an ice pack, or would it be used in a hot pack? Explain briefly.

c. Calorimetry data is collected from an experiment using a bomb calorimeter. Ethanol (C2H5OH (l)) is combusted in the bomb calorimeter, producing liquid water and carbon dioxide gas. During the experiment, the thermal energy of the ethanol is transferred directly to the calorimeter (rather than the water being produced). Therefore, in this case, the quantity of energy transferred is determined using: qbomb = cbomb x T. The mass of ethanol combusted in the calorimeter was 3.26 g. The heat capacity of the bomb calorimeter is 11.7 kJ/oC. The initial temperature of the bomb calorimeter was 21.5 oC, and its final temperature was 29.4 oC. Determine the molar enthalpy of combustion of the ethanol, using the provided calorimetry data. Display the molar enthalpy of combustion value as a part of a balanced reaction equation for the combustion of ethanol.

d. Calculate the molar enthalpy of combustion of ethanol, using standard enthalpies of formation. Briefly explain any discrepancies in your answer for part c compared to part d.