NEET Thermodynamics — Set 13

Question 1

Calculate $\Delta G^\circ$ for a reaction with $K = 10^4$ at 298 K. ($R = 8.314 \, \text{J/mol·K}$)

Accepted Answer

$\Delta G^\circ = -RT \ln K = -8.314 \times 298 \times \ln(10^4) = -8.314 \times 298 \times 9.21 = -22823 \, \text{J/mol} = -22.82 \, \text{kJ/mol}$.

Question 2

For the reaction $H_2(g) + I_2(g) \rightarrow 2HI(g)$, $\Delta H = 52.96 \, \text{kJ/mol}$ at 298 K. What is $\Delta U$? ($R = 8.314 \, \text{J/mol·K}$)

Accepted Answer

$\Delta n_g = 2 - 2 = 0$, so $\Delta H = \Delta U + \Delta n_g RT = \Delta U$. Thus, $\Delta U = 52.96 \, \text{kJ/mol}$.

Question 3

For an ideal gas ($\gamma = 1.33$) compressed adiabatically from 18 L to 6 L at 300 K, what is the final temperature?

Accepted Answer

$T_2 = T_1 (V_1/V_2)^{\gamma-1} = 300 \times (18/6)^{0.33} = 300 \times 3^{0.33} = 300 \times 1.44 = 432 \, \text{K}$.

NEET Chemistry: Thermodynamics — Practice Set 13

Q1. Calculate \(\Delta G^\circ\) for a reaction with \(K = 10^4\) at 298 K. (\(R = 8.314 \, \text{J/mol·K}\))

Q2. For the reaction \(H_2(g) + I_2(g) \rightarrow 2HI(g)\), \(\Delta H = 52.96 \, \text{kJ/mol}\) at 298 K. What is \(\Delta U\)? (\(R = 8.314 \, \text{J/mol·K}\))

Q3. For an ideal gas (\(\gamma = 1.33\)) compressed adiabatically from 18 L to 6 L at 300 K, what is the final temperature?

Q4. For a chemical reaction carried out at constant temperature (ideal-gas approximation) with \( \Delta U = 250 \,\text{J} \) and no change in moles of gas (\( \Delta n_g = 0 \)), what is the change in enthalpy \( (\Delta H) \)?

Q5. For the combustion of 16 g of methane at 298 K (\( \Delta H_c = -890.30 \, \text{kJ/mol} \), molar mass = 16 g/mol), what is \( \Delta U \)? (\( R = 8.314 \, \text{J/mol·K} \))

Q6. For the reaction \(C(s) + O_2(g) \rightarrow CO_2(g)\), \(\Delta H = -393.5 \, \text{kJ/mol}\) at 298 K. What is \(\Delta U\)? (\(R = 8.314 \, \text{J/mol·K}\))

Q7. For a reversible isothermal compression of an ideal gas, the heat absorbed is:

Q8. In an isobaric process, 600 J of heat is supplied, and the system does 200 J of work. What is \(\Delta U\)?

Q9. What is the entropy change when 1 mol of an ideal gas is compressed isothermally from 10 L to 5 L? (\(R = 8.314 \, \text{J/mol·K}\))

Q10. For the reaction \(N_2(g) + O_2(g) \rightarrow 2NO(g)\), \(\Delta H = 180.6 \, \text{kJ/mol}\) at 298 K. What is \(\Delta U\) if the gas behaves ideally? (\(R = 8.314 \, \text{J/mol·K}\))