NEET Thermodynamics — Set 16

Question 1

A system releases $ 760 \, \text{J} $ of heat and performs $ 240 \, \text{J} $ of work. What is the change in internal energy?

Accepted Answer

First Law: $ \Delta Q = \Delta U + \Delta W $. $ \Delta Q = -760 $ (heat released), $ \Delta W = 240 $ (work by system). $ -760 = \Delta U + 240 \Rightarrow \Delta U = -760 - 240 = -1000 \, \text{J} $.

Question 2

A gas expands adiabatically from $ 10 \, \text{atm} $ and $ 5 \, \text{L} $ to $ 2 \, \text{atm} $. What is the final volume? ($ \gamma = 1.33 $)

Accepted Answer

$ P_1 V_1^\gamma = P_2 V_2^\gamma $. $ 10 \times 5^{1.33} = 2 \times V_2^{1.33} $. $ V_2^{1.33} = \frac{10}{2} \times 5^{1.33} = 5 \times 5^{1.33} $. $ 5^{1.33} \approx 9.62 $, $ V_2^{1.33} = 5 \times 9.62 \approx 48.1 $. $ V_2 = (48.1)^{1/1.33} \approx 14.5 \, \text{L} $.

Question 3

What is the primary reason a real gas deviates from the ideal gas equation?

Accepted Answer

Real gases deviate from the ideal gas equation ($ P V = \mu R T $) due to intermolecular forces, which are negligible in ideal gases but significant in real gases, especially at high pressures or low temperatures.

NEET Physics: Thermodynamics — Practice Set 16

Q1. A system releases \( 760 \, \text{J} \) of heat and performs \( 240 \, \text{J} \) of work. What is the change in internal energy?

Q2. A gas expands adiabatically from \( 10 \, \text{atm} \) and \( 5 \, \text{L} \) to \( 2 \, \text{atm} \). What is the final volume? (\( \gamma = 1.33 \))

Q3. What is the primary reason a real gas deviates from the ideal gas equation?

Q4. How many calories are equivalent to \( 4186 \, \text{J} \) of heat? (1 cal = \( 4.186 \, \text{J} \))

Q5. What is the change in internal energy for \( 0.6 \, \text{moles} \) of an ideal gas heated from \( 270 \, \text{K} \) to \( 320 \, \text{K} \) at constant volume? (\( C_v = 20.8 \, \text{J mol}^{-1} \text{K}^{-1} \))

Q6. A system releases \( 870 \, \text{J} \) of heat and performs \( 330 \, \text{J} \) of work. What is the change in internal energy?

Q7. What is the molar specific heat capacity at constant volume for a diatomic gas if \( R = 8.3 \, \text{J mol}^{-1} \text{K}^{-1} \)?

Q8. 0.15 moles of an ideal gas at 320 K expand isothermally from 3 L to 9 L. What is the work done by the gas? (\( R = 8.3 \, \text{J mol}^{-1} \text{K}^{-1} \))

Q9. What is the physical significance of the equation of state in thermodynamics?

Q10. A gas expands adiabatically from \( 2 \, \text{atm} \) and \( 4 \, \text{L} \) to \( 1 \, \text{atm} \). What is the final volume? (\( \gamma = 1.33 \))