Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Heat and Thermodynamics question

2017 · Shift 0 · Q56
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Heat and Thermodynamics
  5. /2017 · Shift 0 · Q56

Heat and Thermodynamics question

2017 · Shift 0 · Q56

JEE MainPhysicsHeat and ThermodynamicsMCQ+4 / −1
CP and Cv are specific heats at constant pressure and constant volume respectively. It is observed that CP – Cv = a for hydrogen gas CP – Cv = b for nitrogen gas The correct relation between a and b is
  1. A
    a = 28 b
  2. B
    a = 1/14 b
  3. C
    a = b
  4. D
    a = 14 b
View written solutionFree

Correct answer: D

  1. For an ideal gas, the difference between molar specific heats is CP−CV=RC_P - C_V = RCP​−CV​=R where RRR is the universal gas constant.

  2. But here the question says specific heats for hydrogen and nitrogen gas, which usually means per unit mass.

  3. For specific heats per unit mass, we use cp−cv=RMc_p - c_v = \frac{R}{M}cp​−cv​=MR​ where MMM is the molar mass of the gas.

  4. For hydrogen gas: MH2=2M_{H_2} = 2MH2​​=2 Hence, a=cp−cv=R2a = c_p - c_v = \frac{R}{2}a=cp​−cv​=2R​

  5. For nitrogen gas: MN2=28M_{N_2} = 28MN2​​=28 Hence, b=cp−cv=R28b = c_p - c_v = \frac{R}{28}b=cp​−cv​=28R​

  6. Now compare aaa and bbb: ab=R/2R/28=282=14\frac{a}{b} = \frac{R/2}{R/28} = \frac{28}{2} = 14ba​=R/28R/2​=228​=14

    Therefore, a=14ba = 14ba=14b

  7. So the correct option is D.

PreviousNext

More from Heat and Thermodynamics

  • The temperature of an open room of volume 30 m3 increases from 17oC to 27oC due to the sunshine. The atmospheric pressure in the room remains 1 × 105 Pa. If Ni and Nf are the number of molecules in the room before and after heating,…2017 · MCQ
  • An external pressure P is applied on a cube at 0oC so that it is equally compressed from all sides. K is the bulk modulus of the material of the cube and α is its coefficient of linear expansion. Suppose we want to bring the cube to…2017 · MCQ
  • A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be 75oC. T is given by:…2017 · MCQ
  • A simple pendulum made of a bob of mass m and a metallic wire of negligible mass has time period 2 s at T=0oC. If the temperature of the wire is increased and the corresponding change in its time period is plotted against its temperature,…2016 · MCQ
  • The ratio of work done by an ideal monoatomic gas to the heat supplied to it in an isobaric process is :2016 · MCQ
  • 200 g water is heated from 40oC to 60oC. Ignoring the slight expansion of water, the change in its internal energy is close to (Given specific heat of water = 4184 J/kg/K) :2016 · MCQ
  • Which of the following shows the correct relationship between the pressure ‘P’ and density ρ of an ideal gas at constant temperature ?2016 · MCQ
  • ′n′ moles of an ideal gas undergoes a process A→B as shown in the figure. The maximum temperature of the gas during the process will be : Includes diagram2016 · MCQ