Thermodynamics and Thermochemistry
Where A and B are non-zero constants. Which of the following is TRUE about this reaction?
(Specific heat of water liquid and water vapour are 4.2 kJ K–1 kg–1 and 2.0 kJ K–1 kg–1; heat of liquid fusion and vapourisation of water are 334 kJ kg–1 and 2491 kJ kg–1, respectively). (log 273 = 2.436, log 373 = 2.572, log 383= 2.583)
The correct option(s) is (are)
If T2 > T1, the correct statement(s) is (are)
(Assume ΔHθ and ΔSθ are independent of temperature and ratio of ln K at T1 to ln K at T2 is greater than . Here H, S, G and K are enthalpy, entropy, Gibbs energy and equilibrium constant, respectively.)
A(g) + B(g) ⇌ AB(g).
The activation energy of the backward reaction exceeds that of the forward reaction by 2RT (in J mol−1). If the pre-exponential factor of the forward reaction is 4 times that of the reverse reaction, the absolute value of ΔGθ (in J mol−1) for the reaction at 300 K is ____.
(Given; ln (2) = 0.7, RT = 2500 J mol−1 at 300 K and G is the Gibbs energy)
H2(g) + O2(g) → H2O(l) ; ΔrH° = –285.8 kJ mol–1 ;
CO2(g) + 2H2O(l) → CH4(g) + 2O2(g) ; ΔrH° = + 890.3 kJ mol–1
Based on the above thermochemical equations, the value of ΔrH° at 298 K for the reaction
C(graphite) + 2H2(g) → CH4(g) will be :
∆fG° [C(graphite)] = 0 kJ mol–1
∆fG° [C(diamond)] = 2.9 kJ mol–1
The standard state means that the pressure should be 1 bar , and substance should be pure at a given temperature. The conversion of graphite [C(graphite)] to diamond [C(diamond)] reduces its volume by 2 × 10–6 m3 mol–1. If C(graphite) is converted to C(diamond) isothermally at T = 298 K, the pressure at which C(graphite) is in equilibrium with C(diamond), is
[Useful information : 1 J = 1 kg m2 s–2 ; 1 Pa = 1 kg m–1 s–2; 1 bar = 105 Pa]
In a second experiment (Expt. 2), 100 mL of 2.0 M acetic acid (Ka = 2.0 × 10−5) was mixed with 100 mL of 1.0 M NaOH (under identical conditions to Expt. 1) where a temperature rise of 5.6 °C was measured.
(Consider heat capacity of all solutions as 4.2 J g−1 K−1 and density of all solutions as 1.0 g mL−1)
Enthalpy of dissociation (in kJ mol−1) of acetic acid obtained from the Expt. 2 is
Match the thermodynamic processes given under Column I with the expressions given under Column II.
|Column I||Column II|
|(A)||Freezing of water at 273 K and 1 atm||(P)||q = 0|
|(B)||Expansion of 1 mol of an ideal gas into a vacuum under isolated conditions||(Q)||w = 0|
|(C)||Mixing of equal volumes of two ideal
gases at constant temperature and
pressure in an isolated container
|(R)||ΔSsys < 0|
|(D)||Reversible heating of H2(g) at 1 atm
from 300 K to 600 K, followed by
reversible cooling to 300 K at 1 atm
|(S)||ΔU = 0|
|(T)||ΔG = 0|
X2O4 (l) → 2XO2 (g)
ΔU = 2.1 k cal, ΔS = 20 cal K–1 at 300 K
ΔG for this reaction will be:
(R = 8.314 kJ mol−1)
A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0°C. As it does so, it absorbs 208J of heat. The values of q and w for the process will be :
(R = 8.314 J/mol K) (In 7.5 = 2.01)
The standard enthalpies of formation of CO2(g), H2O(l) and glucose(s) at 25°C are −400 kJ/mol, −300 kJ/mol and −1300 kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at 25°C is
Assertion Cp − Cv = R, for an ideal gas.
Reason R is the work done when temperature of one mole of an ideal gas is increased by 1°.
Benzene and naphthalene form an ideal solution at room temperature. For this process, the true statement(s) is (are)
Using the data provided calculate the multiple bond energy of a bond in . That energy is (take the bond energy of a bond as)
The reversible expansion of an ideal gas under adiabatic and isothermal conditions is shown in the figure. Which of the following statements (s) is (are) correct?
Assertion Molar entropy of vaporisation of water is different from ethanol.
Reason Water is more polar than ethanol.
The reaction must be
Match the transformations in Column I with appropriate options in Column II
|Column I||Column II|
Reason : The volume occupied by the molecule is zero.
Reason : Chlorine is a pungent smelling gas and it is difficult to solidify it.
One mole of an ideal gas is taken from a to b along two paths denoted by the solid and the dashed lines as shown in the graph below. If the work done along the solid line path is ws and that along the dotted line path is wd, then the integer closest to the ratio is
In a constant volume calorimeter, 3.5 g of a gas with molecular weight 28 was burnt in excess oxygen at 298.0 K. The temperature of the calorimeter was found to increase from 298.0 K to 298.45 K due to the combustion process. Given that the heat capacity of the calorimeter is the numerical value for the enthalpy of combustion of the gas in is
Reason The entropy of formation of gaseous oxygen molecule under the same conditions is zero.
For every chemical reaction at equilibrium, standard Gibbs energy of reaction is zero.
At constant temperature and pressure, chemical reactions are spontaneous in the direction of decreasing Gibbs energy.
(Given : ∆rH°298K = −54.07 kJ mol-1 , ∆rS°298K = 10 JK−1mol−1and R= 8.314 JK−1mol−1; 2.303×8.314×298 = 5705)
(A) 4.98 kJ
(B) 11.47 kJ
(C) −11.47 kJ
(D) 0 kJ
(b) Consider the three solvents of identical molar masses. Match their boiling points with their Kb values:
|Solvent||Boiling point||Kb value|
(D) not defined, because the pressure is not constant
(a) a reversible isobaric expansion from (1.0 atm, 20.0 L) to (1.0 atm,40.0 L);
(b) a reversible isochoric change of state from (1.0 atm, 40.0 L) to (0.5 atm, 40.0 L);
(c) a reversible isothermal compression from (0.5 atm, 40.0 L) to (1.0 atm, 20.0 L)
(I) Sketch with labels each of the processes in the same P-V diagram.
(II) Calculate the total work (W) and the total heat change (q) involved in the above processes.
(III) What will be the values of .
B A = ?
B C = ?
From the calculated value of and , indicate the order of stability of (A), (B) and (C). Write a reasonable reaction mechanism showing all intermediates leading to (A), (B) and (C).