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Chemistry · THERMODYNAMICS
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Chemistry · THERMODYNAMICS
For 3.0 moles of an ideal gas, the temperature is increased by 40.0 K. The difference between the heat absorbed at constant pressure and the heat absorbed at constant volume (\( q_p - q_v \)) is: (Take \( R = 8.314\text{ J mol}^{-1}\text{ K}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
The standard enthalpy of combustion of benzene, \( \text{C}_6\text{H}_6(l) \), is \( -3267.0\text{ kJ mol}^{-1} \). If the standard enthalpies of formation of \( \text{CO}_2(g) \) and \( \text{H}_2\text{O}(l) \) are \( -393.5\text{ kJ mol}^{-1} \) and \( -285.83\text{ kJ mol}^{-1} \) respectively, what is the standard enthalpy of formation (\( \Delta_f H^\ominus \)) of benzene?
Read answer →Chemistry · THERMODYNAMICS
Calculate the work done when \( 56\text{ g} \) of nitrogen gas (assumed ideal) expands isothermally at \( 27^\circ\text{C} \) from a pressure of \( 5\text{ atm} \) to \( 1\text{ atm} \) in a reversible manner. (Molar mass of \( \text{N}_2 = 28\text{ g}\cdot\text{mol}^{-1} \), \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \), \( \ln 5 = 1.609 \))
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements regarding the Third Law of Thermodynamics: (A) The entropy of any pure crystalline substance approaches zero as \( T \rightarrow 0\text{ K} \). (B) The entropy of solutions and supercooled liquids is zero at \( 0\text{ K} \). (C) The third law allows the calculation of absolute values of entropy of pure substances from thermal data. (D) Perfect order exists in pure crystalline solids at absolute zero. Which of the above statements are correct?
Read answer →Chemistry · THERMODYNAMICS
For an irreversible isothermal expansion of an ideal gas, which of the following conditions correctly describes \( \Delta U \) and \( \Delta S_{\text{total}} \)?
Read answer →Chemistry · THERMODYNAMICS
Why is it impossible to determine the lattice enthalpy of an ionic crystal like \( \text{NaCl}(s) \) directly by experiment?
Read answer →Chemistry · THERMODYNAMICS
If the molar enthalpy change for vaporisation of \( 1\text{ mol} \) of water at \( 1\text{ bar} \) and \( 100^\circ\text{C} \) is \( 41.00\text{ kJ mol}^{-1} \), assuming water vapour behaves as an ideal gas (\( R = 8.314\text{ J K}^{-1}\text{ mol}^{-1} \)), the change in internal energy (\( \Delta U \)) is approximately:
Read answer →Chemistry · THERMODYNAMICS
For the combustion of liquid benzene at 298 K according to \( \text{C}_6\text{H}_6(l) + \frac{15}{2}\text{O}_2(g) \rightarrow 6\text{CO}_2(g) + 3\text{H}_2\text{O}(l) \), the difference between the heat evolved at constant pressure (\( q_p \)) and at constant volume (\( q_v \)) is equal to:
Read answer →Chemistry · THERMODYNAMICS
Calculate \( \Delta_r G^\circ \) at \( 298\text{ K} \) for the conversion \( \frac{3}{2}\text{O}_2(g) \rightarrow \text{O}_3(g) \) if \( K_p = 2.47 \times 10^{-29} \). (Given: \( 2.303 \times R \times 298 \approx 5706\text{ J mol}^{-1} \), \( \log(2.47) \approx 0.393 \))
Read answer →Chemistry · THERMODYNAMICS
For the reaction \( 2\text{NH}_3(g) + \text{CO}_2(g) \rightleftharpoons \text{NH}_2\text{CONH}_2(aq) + \text{H}_2\text{O}(l) \) at \( 298\text{ K} \), \( \Delta_r G^\circ = -13.6\text{ kJ mol}^{-1} \). Find the equilibrium constant \( K \). (Given: \( \frac{13.6 \times 10^3}{2.303 \times 8.314 \times 298} = 2.38 \) and \( 10^{0.38} = 2.4 \))
Read answer →Chemistry · THERMODYNAMICS
Consider the following thermochemical reactions: (i) \( \text{C}(\text{graphite}) + \text{O}_2(g) \rightarrow \text{CO}_2(g) \); \( \Delta_r H^\ominus = -393.5\text{ kJ mol}^{-1} \) (ii) \( \text{CO}(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \); \( \Delta_r H^\ominus = -283.0\text{ kJ mol}^{-1} \) Applying Hess's law, the standard enthalpy of formation of \( \text{CO}(g) \) is:
Read answer →Chemistry · THERMODYNAMICS
For the vaporization of \( 1.0\text{ mol} \) of water at \( 100^\circ\text{C} \) and \( 1\text{ bar} \), the enthalpy of vaporization \( \Delta_{\text{vap}}H \) is \( 40.66\text{ kJ}\cdot\text{mol}^{-1} \). Assuming water vapor behaves as an ideal gas and the molar volume of liquid water is negligible, the change in internal energy \( \Delta_{\text{vap}}U \) is: (Take \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
Combustion of 1.0 g of graphite in a bomb calorimeter produces a temperature rise from 298 K to 299 K. If the heat capacity of the calorimeter is \( 20.7\text{ kJ K}^{-1} \), what is the internal energy change (\( \Delta U \)) for the combustion of 1 mol of graphite?
Read answer →Chemistry · THERMODYNAMICS
The standard enthalpy of fusion of ice is \( \Delta_{\text{fus}}H^\ominus = 6.00\text{ kJ mol}^{-1} \) at 273 K. What is the value of standard enthalpy of freezing of water at the same temperature?
Read answer →Chemistry · THERMODYNAMICS
Given that for benzene (\( \text{C}_6\text{H}_6 \)), the standard enthalpy of fusion is \( \Delta_{\text{fus}} H^\ominus = 9.83\text{ kJ mol}^{-1} \) and the standard enthalpy of vaporisation is \( \Delta_{\text{vap}} H^\ominus = 30.80\text{ kJ mol}^{-1} \). The heat required to sublime 0.50 mole of solid benzene under standard conditions is:
Read answer →Chemistry · THERMODYNAMICS
For which of the following processes is the enthalpy of atomization exactly equal to the enthalpy of sublimation?
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements regarding entropy changes: (A) A liquid crystallizing into a solid results in an increase in entropy. (B) The entropy of a crystalline solid at \( 0\text{ K} \) is minimum. (C) In the decomposition \( 2\text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s) + \text{CO}_2(g) + \text{H}_2\text{O}(g) \), entropy increases. (D) For the atomization \( \text{H}_2(g) \rightarrow 2\text{H}(g) \), entropy decreases. Which of the above statements are correct?
Read answer →Chemistry · THERMODYNAMICS
A cylinder containing \( 2\text{ mol} \) of an ideal gas at \( 27^\circ\text{C} \) is compressed by moving a piston inward. If the process is carried out at constant pressure of \( 2\text{ atm} \) and the temperature rises to \( 127^\circ\text{C} \), the work done during this process is: (Take \( R = 8.314\text{ J}\cdot\text{K}^{-1}\cdot\text{mol}^{-1} \))
Read answer →Chemistry · THERMODYNAMICS
Consider the following chemical reactions: (A) \( \text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \to \text{H}_2\text{O}(l) \) (B) \( \text{C}(\text{graphite}) + 2\text{H}_2(g) \to \text{CH}_4(g) \) (C) \( \text{CaO}(s) + \text{CO}_2(g) \to \text{CaCO}_3(s) \) (D) \( \text{H}_2(g) + \text{Br}_2(l) \to 2\text{HBr}(g) \) In how many of the above reactions does the reaction enthalpy (\( \Delta_r H^\ominus \)) directly represent the standard molar enthalpy of formation (\( \Delta_f H^\ominus \)) of the product? Which of the above statements is/are correct?
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements for an ideal gas expanding isothermally: (A) In a reversible isothermal expansion, the process occurs in infinite infinitesimal steps. (B) The work done in isothermal reversible expansion is given by \( w_{\text{rev}} = -2.303\, nRT \log(\frac{V_f}{V_i}) \). (C) For isothermal expansion against vacuum, the work done is maximum. (D) The change in internal energy during isothermal expansion of an ideal gas is zero. Choose the correct answer from the options given below:
Read answer →Chemistry · THERMODYNAMICS
The standard enthalpy of atomization of methane, \( \text{CH}_4(\text{g}) \), is \( 1665\text{ kJ mol}^{-1} \). The mean \( \text{C}-\text{H} \) bond enthalpy in methane is:
Read answer →Chemistry · THERMODYNAMICS
Consider the following statements regarding the thermodynamic expansion of an ideal gas: (A) In a free expansion of an ideal gas into vacuum under isothermal conditions, \( w = 0 \), \( q = 0 \), and \( \Delta U = 0 \). (B) The magnitude of reversible isothermal expansion work is always greater than the magnitude of irreversible expansion work against a constant external pressure between the same initial and final states. (C) For an ideal gas expanding at constant volume, work done is zero and the heat absorbed is exactly equal to the change in enthalpy \( \Delta H \). (D) A reversible process proceeds through a series of equilibrium states such that the system and surroundings are always in near equilibrium with each other. How many of the above statements are correct?
Read answer →Chemistry · THERMODYNAMICS
