Molecular Physics | Thermodynamics Answers

2. The latent heat of the water-steam phase transition at p=1 atm and T=100^oC is 2256 kJ/kg. What is the entropy change delta S as the liquid vaporizes?

A. –22.56 kJ/K-kg

B. -6048 J/K-kg

C. 6048 J/K-kg

D. 22.56 kJ/K-kg

A car mass 1.0x105g travelling at 20m/s is brought to rest by applying the brakes. Assuming that the kinetic energy of the car becomes transferred to internal energy in four steel brake drum of equal mass, find the rise in temperature the drum if the total mass is 20kg, the specific heat capacity of the steel is 450J/kg and the work done is equal on all four drum

EX 5:- 1 The molecular weight of carbon dioxide, CO2

, is 44. In an experiment the value

γ for CO

2 was found to be 1.3. Assuming that CO

2

is a perfect gas, calculate the gas

constant, R, and the specific heats at constant pressure and constant volume, Cp, Cv

(0.189 kJ/kg.K; 0.63kJ/kg.K; 0.819kJ/kg.K).

EX 5:- 1 The molecular weight of carbon dioxide, CO2

, is 44. In an experiment the value

γ for CO

2 was found to be 1.3. Assuming that CO

2

is a perfect gas, calculate the gas

constant, R, and the specific heats at constant pressure and constant volume, Cp, Cv

(0.189 kJ/kg.K; 0.63kJ/kg.K; 0.819kJ/kg.K).

The central deflection of the diaphragm of an elastic type pressure measuring instrument was

found to be 0.25mm of an applied pressure of 106𝑝𝑎. The output displacement of diaphragm

has been fed to a Linear variable differential transducer (LVDT) with a built in amplifier

having a sensitivity of 40V/mm. Finally the output is displayed on an analog voltmeter which

has a radius of scale line as 60mm and has a voltage range from zero to 10 volts in an arc of

1500. Using a well labelled diagram, determine the sensitivity of the given diaphragm gauge

in terms of mm/bar (1 bar=105𝑝𝑎).

A small turbine using compressed air has a power output of 100 W.

The enthalpy of the air at the inlet is 320 kJ/kg and the enthalpy at the outlet is 240 kJ/kg. Assume the process is adiabatic and the change in the kinetic energy is negligible. Compute the mass flow rate.

A sample of helium gas behaves as an ideal gas as energy is added by heat at constant pressure from 273K t 393K. If 20.0J of work is done by the gas during this process, what is the mass of the helium present?

From the knowledge that CV, the molar specific heat at constant volume, for a gas in a container is 5.0R, calculate the ratio of the speed of sound in that gas to the rms speed of the molecules,

for gas temperature T.

A rigid tanks contains a perfect gas with R = 2.08 KJ/kg-K and k = 1.67. Calculate the final temperature in C if it initially at 30C and 15KJ/kg of heat is added

A tank contains 80 of air at a pressure of 350 psi; If the air is cooled until its pressure and temperature decreases to 200 psi and 80F respectively, what is the decrease in internal energy in Btu.