Heat Capacity and Calorimetry - UNSOLVED PRACTICE SET
Chapter: Thermodynamics | Topic: Heat Capacity and Calorimetry
HEAT CAPACITY AND CALORIMETRY - UNSOLVED PRACTICE SET
Topic: Heat Capacity and Calorimetry
Multiple Choice Questions
Q1. Heat capacity (C) of a substance is defined as:
- The amount of heat required to raise the temperature of 1 mole of substance by 1°C
- The amount of heat required to raise the temperature of unit mass of substance by 1°C
- The amount of heat required to raise the temperature of a given amount of substance by 1°C
- The amount of heat released when 1 mole of substance burns completely
Q2. The specific heat capacity of water is 4.18 J/g·°C. This means:
- 4.18 J of heat raises the temperature of 1 g of water by 4.18°C
- 4.18 J of heat raises the temperature of 1 g of water by 1°C
- 1 J of heat raises the temperature of 4.18 g of water by 1°C
- 4.18 J of heat raises the temperature of 4.18 g of water by 1°C
Q3. A coffee cup calorimeter is used to measure:
- ΔU at constant volume
- ΔH at constant pressure
- ΔS at constant temperature
- ΔG at constant pressure
Q4. The heat capacity at constant pressure (Cp) is always:
- Less than the heat capacity at constant volume (Cv)
- Equal to the heat capacity at constant volume (Cv)
- Greater than the heat capacity at constant volume (Cv)
- Unrelated to the heat capacity at constant volume (Cv)
Q5. In a bomb calorimeter, the heat measured corresponds to:
- ΔH at constant pressure
- ΔU at constant volume
- ΔG at constant temperature
- ΔS at constant pressure
Q6. The molar heat capacity of a monoatomic ideal gas at constant volume is:
- R/2
- R
- 3R/2
- 5R/2
Short Answer Questions
Q7. Distinguish between heat capacity and specific heat capacity. Why is specific heat capacity more useful for comparing different substances?
Q8. Explain the principle of a bomb calorimeter. Why is it called a 'constant volume' calorimeter?
Q9. Why does water have a very high specific heat capacity? How does this property affect the climate near large water bodies?
Q10. Derive the relationship between Cp and Cv for an ideal gas. What is the value of Cp – Cv?
Q11. A student uses a coffee cup calorimeter to measure the heat of neutralisation. Why is it important to use a polystyrene (thermocol) cup rather than a metal cup?
Q12. Define molar heat capacity. How does it differ from specific heat capacity? Write the relationship between them.
Long Answer Questions
Q13. (a) Define heat capacity at constant volume (Cv) and heat capacity at constant pressure (Cp).
(b) Show that Cp – Cv = R for an ideal gas.
(c) Explain why Cp is always greater than Cv for gases, but approximately equal for solids and liquids.
Q14. (a) Describe the construction and working of a bomb calorimeter with a neat diagram description.
(b) How would you calculate the heat of combustion of a substance using a bomb calorimeter?
(c) Why is the water equivalent of a calorimeter important? How is it determined?
Q15. (a) Explain the principle of a coffee cup calorimeter. Why is it suitable for measuring enthalpy changes at constant pressure?
(b) A student wants to determine the specific heat capacity of an unknown metal. Describe the experimental procedure step-by-step.
(c) What precautions should be taken to minimize heat loss to the surroundings during a calorimetry experiment?
Numerical / Application-Based Problems
Q16. A 50.0 g piece of copper at 100.0°C is dropped into 100.0 g of water at 20.0°C in a calorimeter. The final temperature of the mixture is 23.5°C.
(a) Calculate the heat lost by the copper.
(b) Calculate the specific heat capacity of copper.
(c) The accepted value for the specific heat capacity of copper is 0.385 J/g·°C. Calculate the percentage error in the student's result.
(Given: Specific heat capacity of water = 4.18 J/g·°C)
Q17. A bomb calorimeter has a heat capacity of 2.50 kJ/°C. When 1.50 g of glucose (C₆H₁₂O₆) is burned in the calorimeter, the temperature rises from 25.00°C to 29.85°C.
(a) Calculate the heat of combustion of glucose at constant volume (ΔU).
(b) Calculate the heat of combustion at constant pressure (ΔH).
(c) Write the thermochemical equation for the combustion of glucose.
(Molar mass of glucose = 180 g/mol, R = 8.314 J/mol·K)
Q18. In a school experiment, a student mixes 100 mL of 0.50 M HCl with 100 mL of 0.50 M NaOH in a coffee cup calorimeter. The initial temperature of both solutions is 22.0°C, and the final temperature is 25.8°C.
(a) Calculate the heat evolved during the reaction.
(b) Calculate the enthalpy change of neutralisation per mole of water formed.
(c) Suggest two sources of error that could cause the experimental value to differ from the standard value of –57.1 kJ/mol.
(Given: Density of solution = 1.0 g/mL, Specific heat capacity = 4.18 J/g·°C)