Write expression for the equilibrium constants for the following reactions:

a) N2(g) + 3H2(g) = 2NH3(g)
b) 2SO2(g) + O2(g) = 2SO3(g)
c) NH3(g) + HCl(g) = NH4Cl(s)

a) k=[NH3]^2/[N2][H2]^3

b) k=[SO3]^2/[SO2]^2[O2]

c) k=[NH3][HCL]

Note: you do not include solids in equilibrium expressions because their activity is always equal to 1