For a solid I would say something like aerogel would have a large volume but very little mass.
Let me know if this helped or not.
Compressions are regions of high pressure due to particles being close together
rarefactions are regions of low pressure due to particles being spread further apart
Longitudinal waves are often demonstrated by pushing and pulling a stretched slinky spring
<u>Answer:</u> The equilibrium constant expression for the given equation is written below.
<u>Explanation:</u>
Equilibrium constant in terms of partial pressure is defined as the ratio of partial pressures of products to the partial pressures of reactants each raised to the power their stoichiometric ratios. It is expressed as 
For the general chemical equation:

The expression of
follows:

For the given chemical equation:

The expression of
for above equation follows:

Hence, the equilibrium constant expression for the given equation is written above.