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MCQs

  1. A gas has a pressure P, volume V and temperature 500 K. The pressure is doubled at constant volume and then the volume is reduced to one quarter at constant pressure. The final temperature of the gas in K is
    a.   125                             
    b.   250                       
    c.   500                       
    d.   1000
  2. At constant temperature, the graph of pressure Vs. reciprocal of volume is
    a.   straight line                
    b.   parabola                
    c.   ellipse                   
    d.   circle
  3. Boyle’s law is applicable in
    a.   isochoric condition                                        
    b.   isothermal condition
    c.   isobaric condition                                          
    d.   isotonic process
  4. At 0 K, which of the following property of gas will be zero?
    a.   K.E.                            
    b.   P.E.                      
    c.   mass                      
    d.   density
  5. A box contains n molecules of gas. If the number of molecules is increased to 2n, the pressure of gas will
    a.   become half                                                   
    b.   becomes 4 times
    c.   remain unchanged                                         
    d.   become twice
  6. How much should the pressure of a gas be increased to decrease the volume of the gas by 10% at constant temperature?
    a.   10%                            
    b.   9.5%                     
    c.   11.11%                 
    d.   5.11
  7. What is the value of PV/T for one mole of ideal gas?
    a.   8.4 cal/molK               
    b.   4.2 cal/molK         
    c.   2 cal/molK            
    d.   none of above
  8. A sample of an ideal gas occupies a volume V at a pressure P and absolute temperature T. The mass of each molecule is m. Which of the following expressions gives the density of the gas?
    a.   mkT                            
    b.   Pm/kT                   
    c.   P/kTV                   
    d.   P/kT
  9. A sample of oxygen have the same mass, volume and pressure as another sample of hydrogen. The ratio of their temperature will be [latex]T_o/T_H[/latex]?
    a.   4                                 
    b.   8                           
    c.   16                         
    d.   32
  10. Pressure of a gas at constant volume is proportional to
    a.   total energy of gas                                          
    b.   average P.E. of molecules
    c.   average K.E. of molecules                             
    d.   total internal energy of gas
Q1
CONCEPTUAL PROBLEMS
  1. How can Kelvin scale, in principle, be designed by the experiment based on ideal gas law? Explain.
  2. What physical concept is provided by universal gas constant? Write its unit.
  3. On reducing the volume of a gas at constant temperature, the pressure of a gas increases. Why?
  4. What is the difference between a real and an ideal gas? Explain on the basis of the hypothesis of the kinetic theory.
  5. Do you expect the gas in cooking as cylinder to obey the ideal gas equation?
  6. What are the characteristics of a gas to be an ideal?
  7. Why does the cycle tube burst sometimes in summer?
  8. What does “the kinetic interpretation of temperature” signify? Explain.
  9. Explain on the basis of kinetic theory that the pressure of a gas increases with increase of temperature.
  10. At a fixed temperature the volume of a vessel in compressed to half. How will the rms speed of the gas in it change?
  11. In the kinetic theory of gases, why do we not take into account the changes in gravitational potential energy of the molecule?
  12. At absolute zero temperature, why is the kinetic energy zero?
  13. Why do you consider an ideal gas while formulating the pressure in the light of kinetic theory of gases?
  14. Outline the essential features of the kinetic theory of gases.
  15. If the pressure of a gas increases by 10%, what is the percentage decrease in volume if Boyle’s law holds good.
Show answer
Correct answer: (B)
Q2
THEOREY BASED PROBLEMS
  1. State Boyle’s and Charle’s law and hence obtain the relationship for the combined gas law.
  2. Derive an expression for the pressure exerted by an ideal gas on the basis of kinetic theory.
  3. What do you mean by ideal gas? Derive PV = mrT, where symbols have usual meanings.
  4. How do you distinguish ideal gas and real gas. Derive P = [latex]\rho rT[/latex] where symbol have usual meaning.
  5. Derive ideal gas equation on the basis of kinetic theory of a gas.
  6. What is perfect gas? Prove that the average kinetic energy of a gas molecule is directly proportional to the absolute temperature of the gas.
Show answer
Correct answer: (A)

Numerical problems

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