Molecular physics

Q₁=100 kJ, Q₂=60 kJ. what is the efficiency this engine machine?

• 0.4%

• 40%

• 60%

• 0.1

There is an oxygen gas in the container at 200kPa pressure. Root mean square speed of the molecules is 400 m/s. What is the molecular concentration ?

• 9.04*10⁹ m^-3

• 2*10¹⁸ m^-3

• 7*10²⁵ m^-3

• 12.71*10¹⁹ m^-3

The volume of a gas increases by 20% when its temperature is increased by 55 ⁰C at constant pressure. What is the initial temperature of the gas?

An ideal gas sample isothermally expands from 0.3 L to 0.8 L. What is the change in the internal energy of the gas during the process, if its initial temperature is 300K?

• 100 J

• 50 J

• 0 J

• -50 J

What is the partial pressure of water vapour in air at 20⁰C, if the relative humidity is 40%? The vapour pressure of water at 20⁰C is P_v=2333 Pa.

• 100 kPa

• 933 Pa

• 88 MPa

• 60 kPa