Find the bulk modulus of the gas...thermal equilibrium problem...

If the equation is
P = aV
or
PV^-1 = a ........α = (-1)
Then we know from Laplace law.
K = αP
Or K = (-1) x av     [ From equation (1)and (2) ]
K = - aV
or K = (-1) x P
K = -P
In the bulk modulus
K = P
Hence the Bulk Modulus of the gas is K = P.