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Chemistry · THERMODYNAMICS
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Chemistry · THERMODYNAMICS
In an experiment, \( 1\text{ mol} \) of an ideal gas at \( 300\text{ K} \) expands from \( 2\text{ L} \) to \( 20\text{ L} \). In case (i), it expands isothermally and reversibly. In case (ii), it expands isothermally against a constant external pressure of \( 1\text{ atm} \). What is the ratio of the magnitude of work done in case (i) to that in case (ii)? (Take \( R = 0.082\text{ L}\cdot\text{atm}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \), \( \ln 10 = 2.303 \))
Read answer →Chemistry · THERMODYNAMICS
For the formation of ammonia from its elements: \( \text{N}_2(g) + 3\text{H}_2(g) \rightarrow 2\text{NH}_3(g) \), the value of \( \Delta H \) is \( -92.4\text{ kJ} \) at \( 27^\circ\text{C} \). The change in internal energy \( \Delta U \) is: (Take \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
Given the following thermochemical data for \( \text{NaCl} \): Sublimation enthalpy of sodium: \( +108.4\text{ kJ mol}^{-1} \) Ionization enthalpy of sodium: \( +496\text{ kJ mol}^{-1} \) Dissociation enthalpy of \( \text{Cl}_2 \): \( +242\text{ kJ mol}^{-1} \) Electron gain enthalpy of chlorine: \( -348.6\text{ kJ mol}^{-1} \) Standard enthalpy of formation of \( \text{NaCl}(s) \): \( -411.2\text{ kJ mol}^{-1} \) What is the lattice enthalpy (\( \Delta_{\text{lattice}} H^\ominus \)) of \( \text{NaCl}(s) \)?
Read answer →Chemistry · THERMODYNAMICS
Which of the following chemical reactions is endothermic yet known to proceed spontaneously under appropriate conditions?
Read answer →Chemistry · THERMODYNAMICS
At temperature \( T \), the relation between the ionization enthalpy (\( \Delta_i H^\ominus \)) and ionization energy (\( E_0 \)) for an atom in gaseous state is:
Read answer →Chemistry · THERMODYNAMICS
Three moles of an ideal gas expand isothermally and reversibly from an initial pressure of \( 10.0\text{ atm} \) to a final pressure of \( 1.0\text{ atm} \) at \( 300\text{ K} \). The work done by the gas is: (Given: \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \), \( \ln 10 = 2.303 \))
Read answer →Chemistry · THERMODYNAMICS
The thermochemical equation for the combustion of ethanol is: \( \text{C}_2\text{H}_5\text{OH}(l) + 3\text{O}_2(g) \rightarrow 2\text{CO}_2(g) + 3\text{H}_2\text{O}(l) \); \( \Delta_r H^\ominus = -1367.0\text{ kJ mol}^{-1} \) at 298 K. The value of \( \Delta_r U^\ominus \) for this reaction at 298 K is: (Take \( R = 8.314\text{ J mol}^{-1}\text{ K}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
A gas is enclosed in a container of volume \( V \) at temperature \( T \) as depicted in the figure. A partition is placed such that the volume is halved into two compartments. What are the volume and temperature of each individual compartment, and which property types do they represent?
Read answer →Chemistry · THERMODYNAMICS
Given the standard molar enthalpies of formation at 298 K: \( \Delta_f H^\ominus[\text{CH}_4(g)] = -74.81\text{ kJ mol}^{-1} \), \( \Delta_f H^\ominus[\text{CO}_2(g)] = -393.51\text{ kJ mol}^{-1} \), and \( \Delta_f H^\ominus[\text{H}_2\text{O}(l)] = -285.83\text{ kJ mol}^{-1} \). The standard enthalpy of combustion of methane, \( \text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(l) \), is:
Read answer →Chemistry · THERMODYNAMICS
According to Hess's Law of Constant Heat Summation, if an overall chemical reaction \( \text{A} \rightarrow \text{B} \) proceeds directly along one path with enthalpy change \( \Delta_r H \), and along an indirect path \( \text{A} \rightarrow \text{C} \rightarrow \text{D} \rightarrow \text{B} \) with intermediate enthalpy changes \( \Delta_r H_1, \Delta_r H_2, \Delta_r H_3 \), which relation is fundamentally obeyed due to enthalpy being a state function?
Read answer →Chemistry · THERMODYNAMICS
The standard reaction enthalpy for the decomposition \( \text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g) \) is \( +178.3\text{ kJ mol}^{-1} \). The amount of heat required to decompose 25.0 g of pure \( \text{CaCO}_3(s) \) (molar mass = \( 100\text{ g mol}^{-1} \)) into \( \text{CaO}(s) \) and \( \text{CO}_2(g) \) under standard conditions is:
Read answer →Chemistry · THERMODYNAMICS
Given below are two statements: Statement I: Standard state of a substance at a specified temperature is defined at a pressure of 1 atm. Statement II: The reference state of an element is its most stable state of aggregation at 25 °C and 1 bar. In the light of the above statements, choose the most appropriate answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
For the dissociation of one mole of \( \text{NaCl(s)} \) into gaseous ions: \( \text{NaCl(s)} \rightarrow \text{Na}^+(\text{g}) + \text{Cl}^-(\text{g}) \), the lattice enthalpy is \( +788\text{ kJ mol}^{-1} \). The corresponding internal energy change (\( \Delta U \)) is smaller than lattice enthalpy by:
Read answer →Chemistry · THERMODYNAMICS
Match List-I with List-II: List-I (Substance) List-II (\( \Delta_{\text{vap}} H^\ominus / \text{kJ mol}^{-1} \)) A \( \text{H}_2\text{O} \) I 16.15 B \( \text{CCl}_4 \) II 29.10 C \( \text{CH}_3\text{COCH}_3 \) III 40.79 D \( \text{HCl} \) IV 30.00 Choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
Given below are two statements:\n Statement I: Heat absorbed by a system at constant volume is equal to the enthalpy change (\( q_v = \Delta H \)).\n Statement II: Heat absorbed by a system at constant pressure is equal to the internal energy change (\( q_p = \Delta U \)). \nIn the light of the above statements, choose the most appropriate answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements regarding standard enthalpy of formation (\( \Delta_f H^\ominus \)): (A) By convention, \( \Delta_f H^\ominus \) of an element in its reference state is taken as zero. (B) \( \Delta_f H^\ominus \) for \( \text{C}(\text{graphite}) \) is zero, while for \( \text{C}(\text{diamond}) \) it is non-zero. (C) \( \Delta_f H^\ominus \) of \( \text{Br}_2(g) \) is zero at 298 K and 1 bar. (D) The reference state of sulfur at 298 K and 1 bar is rhombic sulfur. Choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
When a balanced thermochemical equation is multiplied by a factor of 2, the numerical value of its standard enthalpy of reaction (\( \Delta_r H^\ominus \)):
Read answer →Chemistry · THERMODYNAMICS
The stepwise bond dissociation enthalpies for methane are: \( \text{CH}_4(g) \rightarrow \text{CH}_3(g) + \text{H}(g) \); \( \Delta_{\text{bond}} H_1^\ominus = +427\text{ kJ mol}^{-1} \) \( \text{CH}_3(g) \rightarrow \text{CH}_2(g) + \text{H}(g) \); \( \Delta_{\text{bond}} H_2^\ominus = +439\text{ kJ mol}^{-1} \) \( \text{CH}_2(g) \rightarrow \text{CH}(g) + \text{H}(g) \); \( \Delta_{\text{bond}} H_3^\ominus = +452\text{ kJ mol}^{-1} \) \( \text{CH}(g) \rightarrow \text{C}(g) + \text{H}(g) \); \( \Delta_{\text{bond}} H_4^\ominus = +347\text{ kJ mol}^{-1} \) What is the mean \( \text{C}-\text{H} \) bond enthalpy in methane?
Read answer →Chemistry · THERMODYNAMICS
A thermodynamic process is defined as reversible if:
Read answer →Chemistry · THERMODYNAMICS
In a process, \( 701\text{ J} \) of heat is absorbed by a system and \( 394\text{ J} \) of work is done by the system. The change in internal energy (\( \Delta U \)) for this process is:
Read answer →Chemistry · THERMODYNAMICS
Given the enthalpy changes for dissolving 1 mol of \( \text{HCl}(g) \): \( \text{HCl}(g) + 25\text{ aq.} \rightarrow \text{HCl}\cdot 25\text{ aq.}\quad \Delta H_1 = -72.03\text{ kJ mol}^{-1} \) \( \text{HCl}(g) + 40\text{ aq.} \rightarrow \text{HCl}\cdot 40\text{ aq.}\quad \Delta H_2 = -72.79\text{ kJ mol}^{-1} \) \( \text{HCl}(g) + \infty\text{ aq.} \rightarrow \text{HCl}\cdot \infty\text{ aq.}\quad \Delta H_3 = -74.85\text{ kJ mol}^{-1} \) What is the enthalpy of dilution when a solution containing 1 mol of \( \text{HCl} \) in \( 25\text{ moles} \) of water is diluted to infinite dilution?
Read answer →Chemistry · THERMODYNAMICS
Consider the following thermochemical statements regarding bond enthalpy and lattice enthalpy: (A) Mean bond enthalpy in polyatomic molecules is obtained by dividing total enthalpy of atomization by the number of bonds broken. (B) The lattice enthalpy is directly related to enthalpy of solution by \( \Delta_{\text{sol}}H^\ominus = \Delta_{\text{lattice}}H^\ominus + \Delta_{\text{hyd}}H^\ominus \). (C) Dissolution of an ionic compound is generally favored when its lattice enthalpy is very high compared to its hydration enthalpy. (D) For diatomic molecules, bond dissociation enthalpy is identical to enthalpy of atomization. Which of the above statements are correct?
Read answer →Chemistry · THERMODYNAMICS
