NEET Thermodynamics — Set 4

Question 1

Calculate the heat released when 60 g of ethanol is combusted if $\Delta H_c = -1366.7 \, \text{kJ/mol}$. (Molar mass = 46 g/mol)

Accepted Answer

Moles = $60 / 46 = 1.304 \, \text{mol}$, heat released = $1.304 \times 1366.7 = 1782.2 \, \text{kJ}$.

Question 2

A system releases 700 J of heat and performs 400 J of work on the surroundings. What is $\Delta U$?

Accepted Answer

$\Delta U = q + w$. Here, $q = -700 \, \text{J}$ (heat released), $w = -400 \, \text{J}$ (work done by system), so $\Delta U = -700 - 400 = -1100 \, \text{J}$.

Question 3

For $CO(g) + Cl_2(g) \rightarrow COCl_2(g)$, $\Delta H = -108.3 \, \text{kJ/mol}$, $\Delta S = -137 \, \text{J/K}$ at 298 K, what is $\Delta G$?

Accepted Answer

$\Delta G = \Delta H - T\Delta S = -108.3 - 298 \times (-0.137) = -108.3 + 40.83 = -67.47 \, \text{kJ/mol}$.

NEET Chemistry: Thermodynamics — Practice Set 4

Q1. Calculate the heat released when 60 g of ethanol is combusted if \(\Delta H_c = -1366.7 \, \text{kJ/mol}\). (Molar mass = 46 g/mol)

Q2. A system releases 700 J of heat and performs 400 J of work on the surroundings. What is \(\Delta U\)?

Q3. For \(CO(g) + Cl_2(g) \rightarrow COCl_2(g)\), \(\Delta H = -108.3 \, \text{kJ/mol}\), \(\Delta S = -137 \, \text{J/K}\) at 298 K, what is \(\Delta G\)?

Q4. Which of the following is always true for an isothermal process involving an ideal gas?

Q5. For the process \( \ce{CO(g) + 2H2(g) \rightarrow CH3OH(l)} \), \( \Delta H = -128 \, \text{kJ/mol} \) at 298 K, calculate \( \Delta U \). (\( R = 8.314 \, \text{J/mol·K} \))

Q6. What is the work done when 1 mol of an ideal gas expands isothermally and reversibly from 1 atm to 0.5 atm at 300 K? (\(R = 8.314 \, \text{J/mol·K}\))

Q7. For a system at constant pressure, the heat absorbed is equal to:

Q8. Calculate \(\Delta S_{total}\) when 1 mol of ice melts at 263 K if \(\Delta H_{fus} = 6.01 \, \text{kJ/mol}\) and melting point is 273 K.

Q9. The bond enthalpy of \(O=O\) in \(O_2(g)\) is 498 kJ/mol. What is \(\Delta H_f\) of \(O(g)\)?

Q10. During the isothermal reversible expansion of an ideal gas, the change in internal energy (\(\Delta U\)) is: