NEET Thermodynamics — Set 7

Question 1

Calculate $ \Delta S_{sys} $ for the condensation of 1 mol of ethanol at 351 K. ($ \Delta H_{vap} = 38.6 \, \text{kJ/mol} $)

Accepted Answer

For $ C_2H_5OH(g) \rightarrow C_2H_5OH(l) $, $ \Delta S_{sys} = -\frac{\Delta H_{vap}}{T} = -\frac{38.6 \times 10^3}{351} \approx -110.0 \, \text{J/K·mol} $, as condensation decreases entropy.

Question 2

The enthalpy of neutralization of a strong acid with a strong base is approximately:

Accepted Answer

For strong acid-strong base neutralization, $\Delta H = -57.1 \, \text{kJ/mol}$ due to the formation of water, a constant value under standard conditions.

Question 3

For the reaction $2Cl(g) \rightarrow Cl_2(g)$, what are the signs of $\Delta H$ and $\Delta S$?

Accepted Answer

Bond formation is exothermic ($\Delta H < 0$), and entropy decreases as two particles form one ($\Delta S < 0$).

NEET Chemistry: Thermodynamics — Practice Set 7

Q1. Calculate \( \Delta S_{sys} \) for the condensation of 1 mol of ethanol at 351 K. (\( \Delta H_{vap} = 38.6 \, \text{kJ/mol} \))

Q2. The enthalpy of neutralization of a strong acid with a strong base is approximately:

Q3. For the reaction \(2Cl(g) \rightarrow Cl_2(g)\), what are the signs of \(\Delta H\) and \(\Delta S\)?

Q4. The standard state of carbon used to define enthalpies of formation is:

Q5. For an isolated system with \(\Delta U = 0\), what can be said about \(\Delta S\)?

Q6. For the reaction \( 2A(g) \rightarrow B(g) \), \( \Delta H = -40.00 \, \text{kJ/mol} \), \( \Delta S = -100.0 \, \text{J/K·mol} \) at 300 K. What is \( \Delta G \)?

Q7. For \(C_2H_4(g) + 3O_2(g) \rightarrow 2CO_2(g) + 2H_2O(l)\), \(\Delta H = -1411 \, \text{kJ/mol}\) at 298 K, what is \(\Delta U\)? (\(R = 8.314 \, \text{J/mol·K}\))

Q8. What is the entropy change (\(\Delta S\)) for the vaporization of 18 g of water at 373 K if \(\Delta H_{vap} = 40.79 \, \text{kJ/mol}\)? (Molar mass of \(H_2O = 18 \, \text{g/mol}\))

Q9. Calculate the heat released when 22 g of \( CO_2 \) is formed from \( C(s) + O_2(g) \rightarrow CO_2(g) \). (\( \Delta H = -393.5 \, \text{kJ/mol} \), molar mass of \( CO_2 = 44 \, \text{g/mol} \))

Q10. Calculate \(\Delta H\) for \(C_2H_5OH(l) + 3O_2(g) \rightarrow 2CO_2(g) + 3H_2O(l)\) using: \(\Delta H_f^\circ (C_2H_5OH,l) = -277.7 \, \text{kJ/mol}\), \(\Delta H_f^\circ (CO_2,g) = -393.5 \, \text{kJ/mol}\), \(\Delta H_f^\circ (H_2O,l) = -285.8 \, \text{kJ/mol}\).