NEET Thermodynamics — Set 1

Question 1

Calculate $\Delta S_{surr}$ when 2 mol of water freezes at 273 K if $\Delta H_{fus} = 6.01 \, \text{kJ/mol}$.

Accepted Answer

For freezing, $\Delta H = -n \times \Delta H_{fus} = -2 \times 6.01 = -12.02 \, \text{kJ}$, $\Delta S_{surr} = -\Delta H / T = -(-12.02 \times 10^3) / 273 = 44.03 \, \text{J/K}$.

Question 2

For an ideal gas undergoing reversible adiabatic compression, which relationship holds?

Accepted Answer

In a reversible adiabatic process, $P^{1-\gamma} T^\gamma = \text{constant}$, derived from $PV^\gamma = \text{constant}$ and the ideal gas law.

Question 3

A system at constant volume absorbs 208 J of heat, and its temperature increases from 300 K to 310 K. What is $ C_v $? (1 mol diatomic gas)

Accepted Answer

For a diatomic ideal gas at constant volume, $ \Delta U = q_v = nC_v\Delta T $. Given $ q_v = 208 \, \text{J} $, $ n = 1 \, \text{mol} $, $ \Delta T = 310 - 300 = 10 \, \text{K} $, we get $ 208 = 1 \times C_v \times 10 $, so $ C_v = 208 / 10 = 20.8 \, \text{J/mol·K} $, typical for a diatomic gas ($ C_v \approx 2.5R $).

NEET Chemistry: Thermodynamics — Practice Set 1

Q1. Calculate \(\Delta S_{surr}\) when 2 mol of water freezes at 273 K if \(\Delta H_{fus} = 6.01 \, \text{kJ/mol}\).

Q2. For an ideal gas undergoing reversible adiabatic compression, which relationship holds?

Q3. A system at constant volume absorbs 208 J of heat, and its temperature increases from 300 K to 310 K. What is \( C_v \)? (1 mol diatomic gas)

Q4. Calculate \(\Delta H\) for \(C(s) + 2H_2O(g) \rightarrow CO_2(g) + 2H_2(g)\) using: \(\Delta H_f^\circ (H_2O,g) = -241.8 \, \text{kJ/mol}\), \(\Delta H_f^\circ (CO_2,g) = -393.5 \, \text{kJ/mol}\).

Q5. The standard enthalpy change for the reaction \(N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)\) is given by:

Q6. The enthalpy of combustion of glucose is -2808 kJ/mol. How much heat is released when 90 g of glucose is burnt? (Molar mass of \(C_6H_{12}O_6 = 180 \, \text{g/mol}\))

Q7. Calculate \(\Delta H\) for \(C(s) + \frac{1}{2}O_2(g) \rightarrow CO(g)\) given: \(C(s) + O_2(g) \rightarrow CO_2(g)\), \(\Delta H = -393.5 \, \text{kJ/mol}\); \(CO(g) + \frac{1}{2}O_2(g) \rightarrow CO_2(g)\), \(\Delta H = -283 \, \text{kJ/mol}\).

Q8. The equilibrium constant for a reaction is 100 at 300 K. Calculate \(\Delta G^\circ\). (\(R = 8.314 \, \text{J/mol·K}\))

Q9. Calculate the work done when 1 mol of an ideal gas expands isothermally and reversibly from 5 atm to 1 atm at 300 K. (\(R = 8.314 \, \text{J/mol·K}\))

Q10. Calculate the heat required to raise the temperature of 40 g of water from 25°C to 35°C. (Specific heat of water = 4.18 J/g·K)