Recent questions tagged thermodynamics

Calculate the bond energy of $ C-H$ bond in methane from the following data: \[\] $C(s) + 2H_2(g) \rightarrow CH_4(g);\: \: \: \Delta H = -74.8\: kJ$ \[\] $ H_2(g)\rightarrow 2H(g);\Delta H = 435.4\: kJ$ \[\] $ C(s) \rightarrow C(g);\Delta H = 718.4 \: kJ$

asked Mar 19, 2014 by thanvigandhi_1

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Find the temperature as a function of radius r in case of a cylindrical shell whose inner surface temperature and outer surface temperature are $ \theta_1$ and $ \theta_2$. The inner and outer radii of the cylindrical shell are $r_1$ and $r_2$.

asked Mar 19, 2014 by thanvigandhi_1

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A heat engine absorbs heat q1 from a source at temperature $T_1$ and heat $ q_2$ from a source a temperature $T_2$. Work done is found to be $J(q_1+q_2)$. This is in accordance with

asked Mar 18, 2014 by thanvigandhi_1

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A reaction is non-spontaneous at the freezing point of water but is spontaneous at the boiling point of water, then

asked Mar 18, 2014 by thanvigandhi_1

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In an irreversible process taking place at constant $T$ and $p$ and in which only pressure-volume work is being done, the change in Gibbs free energy $(dG)$ and change in entropy $(dS)$, satisfy the criteria

asked Mar 18, 2014 by thanvigandhi_1

1 answer

If the bond dissociation energies of $XY, X_2 \: and \: Y_2$(all diatomic molecules) are in the ratio of 1:1:0.5 and $ \Delta H_f $ for the formation of XY is -200 kJ/mol. The bond dissociation energy of $X_2$ will be

asked Mar 18, 2014 by thanvigandhi_1

1 answer

Consider the reaction $N_2 + 3H_2 \rightarrow 2NH_3$ carried out at constant temperature and pressure. If $ \Delta H\: and\: \Delta U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true?

asked Mar 18, 2014 by thanvigandhi_1

1 answer

The enthalpy changes for the following processes are listed below \[\] $Cl_2(g) = 2Cl(g),\: \: \: \: \: 242.3\: kJ/mol$ \[\] $I_2(g) = 2I(g), \: \: \: \: \: 151\: kJ/mol$ \[\] $ ICl(g) = I(g) + Cl(g),\: \: \: 211.3 \: kJ/mol$ \[\] $ I_2(s) = I_2(g),\: \: \: \: 62.76\: kJ/mol$ \[\] Given that the standard states for iodine and chlorine are $I_2(g)\: and \: Cl_2(g)$, the standard enthalpy of formation of $ICl(g)$ is

asked Mar 18, 2014 by thanvigandhi_1

1 answer

An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system If $T_i$ is the initial temperature and $T_f$ is the final temperature, which of the following statements is correct?

asked Mar 18, 2014 by thanvigandhi_1

1 answer

The standard enthalpy of formation $(\Delta H_f^{\circ} )\: at\: 298\: K$ for methane, $CH_4(g),$ is -74.8 kJ/mol. The additional information required to determine the average energy for $C-H$ bond formation would be

asked Mar 18, 2014 by thanvigandhi_1

1 answer

In conversion of limestone to lime, \[\] $CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$ \[\] the values of $ \Delta H^{\circ}\: and\: \Delta S^{\circ}$ are 179 kJ/mol and 160.2 J/K respectively at 298 K and 1 bar. Assuming that $ \Delta H^{\circ} \: and \: \Delta S^{\circ}$ do not change with temperature, temperature above which conversion of limestone to lime will be spontaneous is

asked Mar 18, 2014 by thanvigandhi_1

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Identify correct statement regarding spontaneous process

asked Mar 18, 2014 by thanvigandhi_1

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Assuming that water vapor is an ideal gas, the internal energy change ($ \Delta U$) when 1 mole of water is vaporized at 1 bar pressure and $100^{\circ}C$ (molar enthalpy of vaporization of water at 1 bar and 373 K = 41 kJ/mol and R = 8.314 J/Kmol) will be

asked Mar 18, 2014 by thanvigandhi_1

1 answer

Standard entropy of $X_2, Y_2\: and\: XY_3$ are 60, 40 and 50 J/Kmol respectively. For the reaction, \[\] $ \large\frac{1}{2}$$ X_2 + Y_2 \rightarrow XY_3;\: \: \: \: \: \: \: \: \Delta H = -30\: kJ,$ \[\] to be at the equilibrium, the temperature will be

asked Mar 18, 2014 by thanvigandhi_1

1 answer

On the basis of the following thermo chemical data $ [ \Delta G_f^{\circ} (H^+ )(aq) = 0] $ \[\] $H_2O(l) \rightarrow H^+ (aq) + OH^-(aq);\: \: \: \: \: \Delta H = 57.32\: kJ $ \[\] $H_2(g) + \large\frac{1}{2} (g) \rightarrow H_2O(l); \: \: \: \: \: \: \Delta H = -286\: kJ$ \[\] The value of enthalpy of formation of $OH^-\: ion $ at $25^{\circ}C$ is

asked Mar 17, 2014 by thanvigandhi_1

1 answer

The standard enthalpy of formation of $NH_3$ is $-46\: kJ/mol.$ If the enthalpy of formation of $H_2$ from its atoms is $-436\: kJ/mol$ and that of $N_2$ is $-712\: kJ/mol$, the average bond enthalpy of $N-H$ bond in $NH_3$ is

asked Mar 17, 2014 by thanvigandhi_1

1 answer

Which of the following statements is true?

asked Mar 17, 2014 by thanvigandhi_1

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One mole of non-ideal gas undergoes a change of state $(2\: atm, 3.01\: L,\: 95K) \: to\: (4\: atm,\: 5L,\: 245K)$ with change in internal energy, $ \Delta U = 30\: L-atm$. The change in enthalpy of the process in $ L-atm$ is

asked Mar 17, 2014 by thanvigandhi_1

1 answer

Starting with same initial conditions an ideal gas expands from volume $V_1$ to volume $V_2$ in three different paths. The work done by the gas is $W_1$ if process is purely isothermal, $W_2$ if process is purely isobaric and $W_3$, if process is purely adiabatic. Which is correct?

asked Mar 17, 2014 by thanvigandhi_1

1 answer

Heat of combustion of $ CH_4(g), \: C(graphite),\: H_2(g)$ are -20 kcal, -40 kcal and -10 kcal respectively. The heat of formation of methane is

asked Mar 17, 2014 by thanvigandhi_1

1 answer

Given that, $NH_3 + 3Cl_2(g) \rightarrow NCl_3(g) + 3HCl(g);\: \: \: \: \Delta H_1 = -x_1$ \[\] $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g);\: \: \: \: \: \: \: \: \Delta H_2 = -x_2$ \[\] $H_2(g) + Cl_2(g) \rightarrow 2HCl(g);\: \: \: \: \: \: \: \: \Delta H_3 = x_3$ \[\] The heat of formation of $NCl_3(g)$ from the above data is

asked Mar 17, 2014 by thanvigandhi_1

1 answer

1 mole of ideal gas is allowed to expand isothermally from the initial volume of 1L to 10L, the value of $ \Delta U$ for the process is $(R = 2\: cal/Kmol)$

asked Mar 17, 2014 by thanvigandhi_1

1 answer

Given that $C+O_2 \rightarrow CO_2;\: \: \: \: \: \Delta H^{\circ} = -x\: kJ\: and\: 2CO+O_2 \rightarrow 2CO_2; \: \: \: \: \:\Delta H^{\circ} = -y\: kJ$ \[\] The standard enthalpy of formation of carbon monoxide is

asked Mar 17, 2014 by thanvigandhi_1

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Calculate Q for isothermal reversible expansion of one mole of ideal gas from initial pressure of 1 bar to 0.1 bar at a constant temperature of 273 K.

asked Mar 17, 2014 by thanvigandhi_1

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Calculate the value of equilibrium constant for a reaction at 400K \[\] $2NOCl(g)2NO(g) + Cl(g)$ \[\] $ \Delta S$ and $ \Delta H$ are 122 J/Kmol and 77.2 kJ/mol respectively.

asked Mar 17, 2014 by thanvigandhi_1

1 answer

The polymerization of ethylene to linear polyethylene is represented by the reaction \[\] $nCH_2=CH_2 \rightarrow (CH_2-CH_2)_n$ \[\] where $n$ has a large integral value. Given that $ \Delta H_{C=C}$ and $ \Delta H_{C-C}$ at 298 K are 590 and 331 kJ/mol. Calculate the enthalpy of polymerization per mol of ethylene.

asked Mar 17, 2014 by thanvigandhi_1

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In which of the following conditions, is work done on the gas?

asked Mar 17, 2014 by thanvigandhi_1

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Calculate the standard entropy change for a reaction $XY$ if the value of $ \Delta H^{\circ} = 28.4 \: kJ$ and equilibrium constant is $1.8 \times 10^{-7}\: at\: 298\: K$.

asked Mar 16, 2014 by thanvigandhi_1

1 answer

Calculate the standard free energy change for the following reaction \[\] $Zn(s) + Cu^{2+} (aq) \rightarrow Cu(s) + Zn^{2+} (aq)$ \[\] Given that $ \Delta G_f^{\circ}\: for \: Cu^{2+} (aq)\: and \: Zn^{2+} (aq)$ as 65 kJ/mol and -147.2 kJ/mol respectively.

asked Mar 16, 2014 by thanvigandhi_1

1 answer

For the reaction $N_2(g) + 3H_2(g)\rightarrow 2NH_3(g) \Delta H = -95.4 \: kJ\: and\: \Delta S = -198.3\: J/K$ \[\] Calculate the temperature at which free energy change is equal to zero.

asked Mar 16, 2014 by thanvigandhi_1

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Calculate the entropy change when 36 g of liquid water evaporates at $373\: K( \Delta H_{vap} = 40.63\: kJ/mol)$

asked Mar 16, 2014 by thanvigandhi_1

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Calculate the entropy change for the conversion of 1 gm of ice to water at 273 K and one atm pressure. The enthalpy of fusion of ice is 6.025 kJ/mol

asked Mar 16, 2014 by thanvigandhi_1

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Calculate the bond energy of $Cl-Cl$ bond from the following data: \[\] $CH_4(g) + Cl_2(g) \rightarrow CH_3Cl(g) + HCl(g); \Delta H = -100.3\: kJ$. Also the bond energies of $C-H,\: C-Cl,\: H-Cl$ bonds are 413, 326 and 431 kJ/mol respectively.

asked Mar 16, 2014 by thanvigandhi_1

1 answer

Calculate the enthalpy change ($ \Delta H$) of the following reaction: \[\] $2C_2H_2(g) + 5O_2(g) \rightarrow 4CO_2(g) + 2H_2O(g)$ given average bond energies of various bonds, i.e, $C-H,\: CC,\: O=O,\: C=O,\: O-H$ as 414, 814, 499, 724 and 640 kJ/mol respectively.

asked Mar 16, 2014 by thanvigandhi_1

1 answer

Calculate standard internal energy change($ \Delta E^{\circ}$) for the reaction \[\] $OF2(g) + H_2O(g) \rightarrow O_2(g) + 2HF(g)$ \[\] Given standard enthalpies of formation $ \Delta H_f^{\circ}\: of\: OF_2(g), H_2O(g)\: and\: HF(g)$ are23, -241.8 and -268.6 kJ/mol respectively.

asked Mar 16, 2014 by thanvigandhi_1

1 answer

2.5 mol of ideal gas at 2 atm and $27^{\circ}C$ expands isothermally to 2.5 times of its original volume against the external pressure of 1 atm. Calculate q

asked Mar 16, 2014 by thanvigandhi_1

1 answer