NEET Thermodynamics — Set 22

Question 1

0.5 kg of a substance at 15°C absorbs 1800 J of heat at constant volume, reaching 45°C. What is its specific heat capacity?

Accepted Answer

Specific heat: $ s = \frac{\Delta Q}{m \Delta T} $. $ \Delta Q = 1800 \, \text{J} $, $ m = 0.5 \, \text{kg} $, $ \Delta T = 45 - 15 = 30 \, \text{K} $. $ s = \frac{1800}{0.5 \times 30} = 120 \, \text{J kg}^{-1} \text{K}^{-1} $.

Question 2

A gas is compressed adiabatically, doing 300 J of work on the system. What is the change in internal energy?

Accepted Answer

For adiabatic ($ \Delta Q = 0 $), First Law: $ \Delta U = -\Delta W $. Work on system: $ \Delta W = -300 \, \text{J} $ (negative by convention). $ \Delta U = -(-300) = 300 \, \text{J} $.

Question 3

How much heat is required to vaporize $ 2 \, \text{g} $ of water at $ 100^\circ \text{C} $ and $ 1 \, \text{atm} $? (Latent heat = $ 2256 \, \text{J/g} $)

Accepted Answer

$ \Delta Q = m L $. $ m = 2 $, $ L = 2256 $. $ \Delta Q = 2 \times 2256 = 4512 \, \text{J} $.

NEET Physics: Thermodynamics — Practice Set 22

Q1. 0.5 kg of a substance at 15°C absorbs 1800 J of heat at constant volume, reaching 45°C. What is its specific heat capacity?

Q2. A gas is compressed adiabatically, doing 300 J of work on the system. What is the change in internal energy?

Q3. How much heat is required to vaporize \( 2 \, \text{g} \) of water at \( 100^\circ \text{C} \) and \( 1 \, \text{atm} \)? (Latent heat = \( 2256 \, \text{J/g} \))

Q4. A system absorbs 850 J of heat and has 300 J of work done on it. What is the change in internal energy?

Q5. In an isothermal process for an ideal gas, what happens to the internal energy?

Q6. What is the change in internal energy for \( 0.8 \, \text{moles} \) of an ideal gas heated from \( 310 \, \text{K} \) to \( 370 \, \text{K} \) at constant volume? (\( C_v = 20.8 \, \text{J mol}^{-1} \text{K}^{-1} \))

Q7. A diatomic gas undergoes an adiabatic expansion from \( 760 \, \text{K} \) to \( 380 \, \text{K} \) with \( 0.8 \, \text{moles} \). What is the work done? (\( R = 8.3 \, \text{J mol}^{-1} \text{K}^{-1} \), \( \gamma = 1.4 \))

Q8. Which thermodynamic process involves a constant temperature?

Q9. Why is the concept of thermal equilibrium essential to the Zeroth Law of Thermodynamics?

Q10. Which of the following is incorrect about reversible processes?