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RSS, June 08, 2006

Calibration problems

1. A calorimeter was calibrated using an electric heating coil. The coil provided 22.5 kJ of heat directly to the calorimeter and the resulting temperature change was from 22.45 °C to 23.97 °C. What is the heat capacity of the calorimeter?

2. A benzoic acid (HC₇H₅O₂; MM = 122.1 g/mol) sample weighing 1.236 g was burned in a calorimeter causing a temperature rise of 2.345 K. The heat of combustion of benzoic acid is -3227 kJ/mol. What is the heat capacity of the calorimeter?

3. A calorimeter was calibrated by reacting 25.0 mL of 2.00 M NaOH with 25.0 mL of 2.00 HCl. The enthalpy change for this (neutralization) reaction is -55.8 kJ/mol. The temperature rose 11.6 K in the reaction. What is the heat capacity of the calorimeter?

Measuring heats of reaction:

4. The heat capacity of a calorimeter is known to be 488 J/K. When 25.0 mL of 0.700 M NaOH was mixed with 25.0 mL of 0.700 M HCl the temperature changed from 21.0 °C to 23.1 °C. How much heat was given off in this neutralization reaction and what is the molar enthalpy change?

5. A sample of 0.100 g of magnesium (at. wt. = 24.3) was dissolved in 50.0 mL of 2.00 M HCl causing a temperature rise of 8.5 K. The heat capacity of the calorimeter was 240 J/K. What is the molar heat of the reaction: Mg(s) + 2 HCl(aq) --> MgCl₂(aq) + H₂(g)? [Note: Mg is the LR.]

6. A 0.461 g sample of naphthalene (C₁₀H₈: MM = 128.2 g/mol) was burned in a calorimeter that has a heat capacity of 9.44 kJ/K. The resulting temperature rise was 1.965 K. What is the heat of combustion of naphthalene?

Solutions are available here.

© 2006 by Dr. Ronald S. Strange