Thermodynamics

[figure] Consider the figure provided. 1 mol of an ideal gas is kept in a cylinder, fitted with a piston, at the position A, at 18°C. If the piston is moved to position B, keeping the temperature unchanged, then 'x' L atm work is done in this reversible process. x = L atm. (nearest integer) [Given : Absolute temperature = °C + 273.15, R = 0.08206 L atm mol-1 K-1]

vapH for water is +40.79 kJ mol-1 at 1 bar and 100 C. Change in internal energy for this vapourisation under same condition is kJ mol-1. (Integer answer) (Given R = 8.3 JK-1 mol-1)

An ideal gas, Cv = 52R, is expanded adiabatically against a constant pressure of 1 atm until it doubles in volume. If the initial temperature and pressure is 298 K and 5 atm, respectively then the final temperature is K (nearest integer). [ cv is the molar heat capacity at constant volume]

For the reaction at 298 K, 2A + B C, H = 400 kJ mol-1 and S = 0.2 kJ mol-1 K-1. The reaction will become spontaneous above K.

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R) In the light of the above statements, choose the correct answer from the options given below.

1. (A) is true but (R) is false
2. Both (A) and (R) are true and (R) is the correct explanation of (A)
3. Both (A) and (R) are true but (R) is not the correct explanation of (A)
4. (A) is false but (R) is true

The heat of combustion of solid benzoic acid at constant volume is -321.30 kJ at 27 C. The heat of combustion at constant pressure is (-321.30 - xR) kJ, the value of x is .

Combustion of 1 mole of benzene is expressed as C6H6(l) + 152O2(g) 6CO2(g) + 3H2O(l). The standard enthalpy of combustion of 2 mol of benzene is −'x' kJ. x = . Given : 1. Standard Enthalpy of formation of 1 mol of C6H6(l), for the reaction 6C(graphite) + 3H2(g) C6H6(l) is 48.5 kJ mol-1. 2. Standard Enthalpy of formation of 1 mol of CO2(g), for the reaction C(graphite) + O2(g) CO2(g) is -393.5 kJ mol-1. 3. Standard Enthalpy of formation of 1 mol of H2O(l), for the reaction H2(g) + 12O2(g) H2O(l) is -286 kJ mol-1.

The enthalpy of formation of ethane (C2H6) from ethylene by addition of hydrogen where the bond-energies of C-H, C-C, C=C, H-H are 414 kJ, 347 kJ, 615 kJ and 435 kJ respectively is − kJ

Three moles of an ideal gas are compressed isothermally from 60 L to 20 L using constant pressure of 5 atm. Heat exchange Q for the compression is - Lit. atm.

Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following :

1. q = 0, T = 0, w = 0
2. q = 0, T 0, w = 0
3. q 0, T = 0, w = 0
4. q = 0, T < 0, w 0