Calorimetry is a method used to measure changes in enthalpy, or heat, that occur

Question

Calorimetry is a method used to measure changes in enthalpy, or heat, that occur during chemical processes. Two common calorimeters are constant-pressure calorimeters and constant-volume (or "bomb") calorimeters. Bomb calorimeters are used to measure combustion and other gas-producing reactions, in which the reaction is observed in a strong, sealed vessel. A simple constant-pressure calorimeter can be made from a foam coffee cup and a thermometer, in which energy changes in a reaction are observed via the change in temperature of the solution in the cup. The idea behind calorimeters is that if they are sufficiently insulated from the outside environment, any energy gained or lost in the chemical reaction will be directly observable as a temperature and/or pressure change in the calorimeter.
  

In the following experiment, a coffee-cup calorimeter containing 100 mL of H2O is used. The initial temperature of the calorimeter is 23.0 C. If 3.60 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution Hsoln of CaCl2 is 82.8 kJ/mol.

Express your answer with the appropriate units.

Explanation / Answer

3.6 g CaCl2 x (1 mol / 111 g) = 0.0324 mol

0.0324 mol CaCl2 x (82.8 kJ / mol) x (1000 J / kJ) = 2685.40 J

Assume that the heat capacity of the solution is the same as that of water (4.184 J/gC)

heat = mass x specific heat x delta T

delta T = heat / (mass x specific heat)

delta T = 2685.40 / (100 x 4.184) = 6.4182 ºC

Final temp should be 23 + 6.4182= 29.41 ºC

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.