Polar bond is formed by 2 non-metal atoms which have a significant difference in electronegativity.
When a substance melts, the solid gains heat, and the motion of the particles increases (particles move faster in liquid form than in solid form).
An adiabatic process is when the system is insulated that no heat is released to the surroundings. For this type of process, we have a derived formula written below:
(T₂/T₁)^C = (V₁/V₂)
where C = Cv/nR
From the complete problem shown in the attached picture, Cv = (3/2)R. Thus,
C= (3/2)/1 mol = 3/2
(T₂/305 K)^(3/2) = (8.5 L/82 L)
Solving for T₂,
<em>T₂ = 67.3 K</em>
I think it's D but not sure