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Chemistry · THERMODYNAMICS
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Chemistry · THERMODYNAMICS
At \( 300\text{ K} \), for the reaction \( \text{PCl}_5(g) \rightarrow \text{PCl}_3(g) + \text{Cl}_2(g) \), the value of \( \Delta H \) is \( +124.7\text{ kJ} \). What is the value of \( \Delta U \) for this reaction at the same temperature? (Take \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
In a bomb calorimeter experiment, the chemical reaction takes place at constant volume. What is the value of work done (\( w \)) during such a process?
Read answer →Chemistry · THERMODYNAMICS
For the formation reaction \( \text{H}_2(g) + \text{Br}_2(l) \rightarrow 2\text{HBr}(g) \), the reaction enthalpy is \( \Delta_r H^\ominus = -72.8\text{ kJ} \). The enthalpy change for the formation of 4.0 moles of \( \text{HBr}(g) \) from its elements in their standard reference states is:
Read answer →Chemistry · THERMODYNAMICS
A film of 36.0 g of water evaporates at 298 K. Given that the standard enthalpy of vaporisation of water at 298 K is \( \Delta_{\text{vap}} H^\ominus = 44.01\text{ kJ mol}^{-1} \) and \( R = 8.314\text{ J mol}^{-1}\text{ K}^{-1} \), the change in internal energy (\( \Delta_{\text{vap}} U \)) for the evaporation of this water film is: (Assume steam behaves as an ideal gas)
Read answer →Chemistry · THERMODYNAMICS
The standard entropy of a pure substance at \( 298\text{ K} \) can be determined from heat capacity data down to \( 0\text{ K} \) using the Third Law of Thermodynamics by evaluating:
Read answer →Chemistry · THERMODYNAMICS
Using the bond enthalpies: \( \Delta_{\text{bond}}H^\ominus(\text{N}\equiv\text{N}) = 946\text{ kJ mol}^{-1} \), \( \Delta_{\text{bond}}H^\ominus(\text{H}-\text{H}) = 435\text{ kJ mol}^{-1} \), and mean bond enthalpy of \( \text{N}-\text{H} = 389\text{ kJ mol}^{-1} \), the standard enthalpy change for \( \text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightarrow 2\text{NH}_3(\text{g}) \) is:
Read answer →Chemistry · THERMODYNAMICS
During an irreversible expansion of an ideal gas from an initial volume of \( 3.0\text{ L} \) to a final volume of \( 8.0\text{ L} \) against a constant external pressure of \( 2.5\text{ bar} \), the gas absorbs \( 750\text{ J} \) of heat. Given \( 1\text{ L}\cdot\text{bar} = 100\text{ J} \), the change in internal energy (\( \Delta U \)) of the gas is:
Read answer →Chemistry · THERMODYNAMICS
Given the following thermochemical equations: (i) \( \text{C}(\text{graphite}) + \text{O}_2(g) \to \text{CO}_2(g);\; \Delta_r H^\ominus = -393.5\text{ kJ mol}^{-1} \) (ii) \( \text{CO}(g) + \frac{1}{2}\text{O}_2(g) \to \text{CO}_2(g);\; \Delta_r H^\ominus = -283.0\text{ kJ mol}^{-1} \) The enthalpy change for \( \text{C}(\text{graphite}) + \frac{1}{2}\text{O}_2(g) \to \text{CO}(g) \) is:
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A system undergoes an adiabatic process where \( 1.5\text{ kJ} \) of work is done by the system. In another step, an electrical work of \( 500\text{ J} \) is done on the same system while it absorbs \( 800\text{ J} \) of heat. The net change in the internal energy of the system across the entire two-step process is:
Read answer →Chemistry · THERMODYNAMICS
When two non-reacting ideal gases, A and B, in an isolated container initially separated by a partition are allowed to diffuse into each other by removing the partition, what are the values of \( \Delta H \) and the entropy change \( \Delta S \) of the system?
Read answer →Chemistry · THERMODYNAMICS
Based on the thermodynamic data summarized in Table 5.4, under which combination of enthalpy and entropy change is a reaction nonspontaneous at all temperatures?
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements regarding thermodynamic variables: (A) Pressure (\( p \)), volume (\( V \)), and temperature (\( T \)) are state variables. (B) The values of state functions depend only on the initial and final states of the system. (C) Heat (\( q \)) and work (\( w \)) are state functions. (D) The absolute value of the internal energy of a system can be readily determined by simple physical measurements. Which of the above statements are correct?
Read answer →Chemistry · THERMODYNAMICS
At \( 60^\circ\text{C} \) and \( 1\text{ atm} \), \( \text{N}_2\text{O}_4(g) \) is \( 50\% \) dissociated into \( \text{NO}_2(g) \). What is the equilibrium constant \( K_p \)?
Read answer →Chemistry · THERMODYNAMICS
The standard enthalpy of combustion of butane (\( \text{C}_4\text{H}_{10} \)) is \( -2658.0\text{ kJ mol}^{-1} \). The amount of heat liberated during the complete combustion of \( 14.5\text{ g} \) of butane is:
Read answer →Chemistry · THERMODYNAMICS
Given the thermochemical reaction: \( \text{C}(\text{graphite}, s) + 2\text{S}(l) \rightarrow \text{CS}_2(l) \); \( \Delta_r H^\ominus = +128.5\text{ kJ mol}^{-1} \). What quantity of heat is absorbed when \( 38\text{ g} \) of carbon disulfide is synthesized from graphite and liquid sulfur?
Read answer →Chemistry · THERMODYNAMICS
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The molar heat capacity of a substance is an intensive property. Reason (R): The ratio of two extensive properties is an intensive property. In the light of the above statements, choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
Two moles of an ideal gas at \( 27^\circ\text{C} \) expand isothermally against a constant external pressure of \( 1.5\text{ atm} \) from \( 5\text{ L} \) to \( 15\text{ L} \). Then, the gas is compressed back to \( 5\text{ L} \) isothermally and reversibly at the same temperature. What is the net work done in the entire cyclic path? (Use \( R = 0.0821\text{ L}\cdot\text{atm}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \), \( \ln 3 = 1.10 \))
Read answer →Chemistry · THERMODYNAMICS
For a strongly endothermic reaction, the value of \( \Delta_r H^\circ \) is large and positive. Under standard conditions, what is the expected magnitude of the equilibrium constant \( K \)?
Read answer →Chemistry · THERMODYNAMICS
If the equilibrium constant for a reaction is \( K = 1 \), what is the value of the standard Gibbs energy change \( \Delta_r G^\circ \)?
Read answer →Chemistry · THERMODYNAMICS
Match List-I with List-II: List-I (Process / State) List-II (Thermodynamic Criterion) A Isolated system at equilibrium I \( \Delta G < 0 \) at constant \( T, p \) B Spontaneous process II \( \Delta S = 0 \) and entropy is maximum C Reversible process III \( S = 0 \) for pure crystal D Absolute zero (0 K) IV \( \Delta S_{\text{total}} = 0 \) Choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
For a chemical reaction at temperature \( T \), the expression for \( \ln K \) in terms of standard enthalpy and entropy change is:
Read answer →Chemistry · THERMODYNAMICS
Match List-I with List-II based on mean bond enthalpies at 298 K: List-I (Bond Type) List-II (Mean Bond Enthalpy in kJ mol-1) A \( \text{C}-\text{C} \) I \( 837 \) B \( \text{C}=\text{C} \) II \( 347 \) C \( \text{C}\equiv\text{C} \) III \( 1070 \) D \( \text{C}\equiv\text{O} \) IV \( 611 \) Choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
