Which of the following is not correct?
(a) ∆G is zero for a reversible reaction.
(b) ∆G is positive for a spontaneous reaction
(c) ∆G is negative tor a spontaneous reaction
(d) ∆G is positive for a non-spontaneous reaction.
(b) ∆G gives a criterion for spontaneity at constant pressure and temperature.
(i) If ∆G is negative (< 0). the process is spontaneous.
(ii) If ∆G is positiv e (> 0). the process is non-spontaneous.
(iii) If ∆G is zero then reaction is at equilibrium.
Consider the following reaction between zinc and oxygen and choose the correct options out of the options given below:
2Zn(s) + 02(g) → 2ZnO(s); ∆H=-693.8 kJ mol-1
(i) The enthalpy of two moles ZnO is less than the total enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ.
(ii) The enthalpy of two moles of ZnO is more than the total enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ.
(iii) 8 kJ mol -1 energy is evolved in the reaction.
(iv) 693.8 kJ mol-1 energy is absorbed in the reaction.
Give reason for the following:
(a)Neither q nor w is a state function but q + w is a state function.
(b)A real crystal has more entropy than an ideal crystal.
The entropy change can be calculated by using the expression ∆S = q rev / T. When water freezes in a glass beaker, choose the correct statement amongst the following:
When water freezes in a glass beaker, choose the correct statement amongst the following:
(a) ∆S(system) decreases but ∆S(surroundings) remains the same.
(b) ∆S(system) increases but ∆S(surroundings) decreases.
(C) ∆S(system) decreases but ∆S(surroundmgs) increases.
(d) ∆S(system) decreases but ∆S(surroundings) also decreases.
The enthalpy of atomisation for the reaction CH4(g) → C(g) + 4H(g) is 1665 kJ mol-1. What is the bond energy of C – H bond?
In an exothermic reaction, heat is evolved, and system loses heat to the surroundings. For such system
(a) qP will be negative
(b) ∆γHwill be negative
(c) qp will be positive
(d) ∆γHwill be positive.
Define the following:
(i) First law of thermodynamics.
(ii) Standard enthalpy of formation.
What is the enthalpy of formation of the most stable form of an element in its standard state?
1 g of graphite is burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atmospheric pressure according to the equation C(graphite) + 02 (g) —> C02 (g) During the reaction, temperature rises from 298 K to 299 K. If the heat capacity of the bomb calorimeter is 20.7 kJ/K, what is the enthalpy change for the above reaction at 298 K and 1 atm?
In an adiabatic process, no transfer-of heat takes place between system and surroundings. Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following.
When two moles of C2H6(g) are burnt, 3129 kj of heat is liberated. Calculate the heat of formation of C2H6(g). ∆fH for C02(g) and H20(l) are-393.5 and -286 kj mol-1 respectively.
How are internal energy change, free energy change and entropy change are related to one another?
Heat capacity (CP) is an extensive property but specific heat (c) is an intensive property. What will be the relation between Cp and c for 1 mol of water?
The spontaneity means, having the potential to proceed without the assistance of external agency. The processes which occur spontaneously are
(a) flow of heat from colder to warmer body.
(b) gas in a container contracting into one comer.
(c) gas expanding to fill the available volume.
(d) burning carbon in oxygen to give carbon dioxide.
The difference between Cp and Cv can be derived using the empirical relation H = U + pV. Calculate the difference between Cp and Cv for 10 moles of an ideal gas.
The net enthalpy change of a reaction is the amount of energy required to break all the bonds in reactant molecules minus amount of energy required to form all the bonds in the product molecules. What will be the enthalpy change for the following reaction?
H2(g) + Br2(g)→2HBr(g)
Given that bond energy of H2, Br2 and HBr is 4.35 kJ mol-1,192 kJ mol-1 and 368 kJ mol -1 respectively.
Give a relation between entropy change and heat absorbed or evolved for a reversible reaction occurring at temperature T.
One mole of acetone requires less heat to vapourise than 1 mol of water. Which of the two liquids has higher enthalpy of vapourisation?
Increase in enthalpy of the surroundings is equal to decrease in enthalpy of the system. Will the temperature of system and surroundings be the same when they are in thermal equilibrium?
Identify the state functions and path functions out of the following: enthalpy, entropy, heat, temperature, work, free energy.
Although heat is a path function but heat absorbed by the system under certain specific conditions is independent of path. What are those conditions? Explain.
Calculate the standard enthalpy of formation of CH3OH. from the following data:
(i) CH3OH(l) + 3/2 02 (g) ———-> CO2 (g) + 2H20 (l); ∆rH– = – 726kj mol-1
(ii) C(s) + 02(g) —————>C02 (g); ∆cH– = -393 kj mol-1
(iii) H2(g) + 1/202(g) —————->H20 (l); ∆fH– = -286 kj mol-1
Which of the following is not correct?
(a) ∆G is zero for a reversible reaction.
(b) ∆G is positive for a spontaneous reaction
(c) ∆G is negative tor a spontaneous reaction
(d) ∆G is positive for a non-spontaneous reaction.
Heat has randomising influence on a system and temperature is the measure of average chaotic motion of particles in the system. Write the mathematical relation which relates these three parameters.
A sample of 1.0 mol of a monoatomic ideal gas is taken through a cyclic process of expansion and compression as shown in the figure. What will be the value of ΔHfor the cycle as a whole?
Calculate the enthalpy change for the reaction: H2(g) + Cl2(g) ————-> 2HCl(g). Given that bond energies ofH-H, Cl- Cl and H-Cl bonds are 433, 244 and 431 kj mol-1 respectively.
Why standard entropy of an elementary substance is not zero whereas standard enthalpy of formation is taken as zero?
Enthalpy of sublimation of a substance is equal to
(a) enthalpy of fusion + enthalpy of vapourisation
(b) enthalpy of fusion
(c) enthalpy of vapourisation
(d) twice the enthalpy of vapourisation.
In a process, 701 ] of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?
Calculate the enthalpy change on freezing of 1.0 mol of water at 10.0 °C to ice at – 10.0 °C. A, H = 6.03 KJ mot1 at 0 °C. Cp [H20(l)J = 75.3 J mol-1 K-1; Cp [H20(s)J = 36.8 J mol-1 K-1.
