Question

When helium is allowed to expand into vacuum, heating effect is observed. Its reason is that

• A. helium is an ideal gas
• B. helium is an inert gas
• C. inversion temperature of helium is low
• D. the boiling point of helium is the lowest amongst the element

Answer 1

The correct option is C inversion temperature of helium is low

When helium gas is allowed to expand into vacuum, the heating effect is observed.
This is because the inversion temperature of helium is very low.
when a gas is present above the inversion temperature heating is observed.
As inverion temperature is low, the gas is present above the inversion temperature and heating is observed.
Hydrogen and helium exhibit heating effect during Joule - Thomson expansion as work of expansion (during adiabatic expansion)