31. A mixture of ideal gases has the following composition by mass :
    

    N2	O2	CO2
    60%	30%	10%

    
    If the universal gas constant is 8314 J/kmolK, the characteristic gas constant of the mixture (in J/kgK) is _______.

1. 1. 274.996

   
   
   

   2. 247.996

   
   
   

   3. 374.996

   
   
   

   4. 174.996

   
   
   

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1. View Hint View Answer Discuss in Forum

   Gas constant of mixture,
   

   Rm =	Universal gas constant
   	Average molar mass

   
   

   Rm =	Universal gas constant
   	Average molar mass

   
   

   Average molar mass =	100						= 30.233 kg/kmol
   	60	+	30	+	10
   	28		32		44

   
   

   Rm =	8314	= 274.996 J/kg -K
   	30.233

   
   

   Correct Option: A

   Gas constant of mixture,
   

   Rm =	Universal gas constant
   	Average molar mass

   
   

   Rm =	Universal gas constant
   	Average molar mass

   
   

   Average molar mass =	100						= 30.233 kg/kmol
   	60	+	30	+	10
   	28		32		44

   
   

   Rm =	8314	= 274.996 J/kg -K
   	30.233

   
   

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32. For an ideal gas with constant values of specific heats, for calculation of the specific enthalpy,
    

1. 1. it is sufficient to know only the temperature
      

   
   
   

   2. both temperature and pressure are required to be known
      

   
   
   

   3. both temperature and volume are required to be known
      

   
   
   

   4. both temperature and mass are required to be known

   
   
   

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1. View Hint View Answer Discuss in Forum

   it is sufficient to know only the temperature
   

   Correct Option: A

   it is sufficient to know only the temperature
   

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33. A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m³. It expands quasistatically at constant temperature to a final volume of 0.030 m³. The work output (in kJ) during this process will be
    

1. 1. 8.32
      

   
   
   

   2. 12.00
      

   
   
   

   3. 554.67
      

   
   
   

   4. 8320.00

   
   
   

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1. View Hint View Answer Discuss in Forum

   W = P1V1 ln	V2	= 8.317 kJ
   	V1

   Correct Option: A

   W = P1V1 ln	V2	= 8.317 kJ
   	V1

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34. A reversible thermodynamic cycle containing only three processes and producing work is to be constructed. The constraints are:
    (i) there must be one isothermal process,
    (ii) there must be one isentropic process,
    (iii) the maximum and minimum cycle pressures and the clearance volume are fixed, and
    (iv) polytropic processes are not allowed. Then the number of possible cycles are
    

1. 1. 1
      

   
   
   

   2. 2
      

   
   
   

   3. 3
      

   
   
   

   4. 4

   
   
   

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1. View Hint View Answer Discuss in Forum

   1

   Correct Option: A

   1

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35. An isolated thermodynamic system executes a process. Choose the correct statement (s) from the following
    

1. 1. No heat is transferred
      

   
   
   

   2. No work is done
      

   
   
   

   3. No mass flows across the boundary of the system
      

   
   
   

   4. No Chemical reaction takes place within the system

   
   
   

   5. ( a , b , c )

   
   
   

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1. View Hint View Answer Discuss in Forum

   For an isolated system, Q = 0, W = 0 and mass does not flow through the system.

   Correct Option: E

   For an isolated system, Q = 0, W = 0 and mass does not flow through the system.

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