We investigate the inviscid compressible flow (Euler) equations constrained by an equation of state (EOS) whose functional form is an arbitrary function of density. Under the aforementioned condition, we interrogate the scale-invariance of the inviscid Euler equations using symmetry methods. We find that under general conditions, we can reduce the inviscid Euler equations into a system of two coupled ordinary differential equations. To test these results, we formulate a classical Noh problem, where the EOS is still an arbitrary function of density. In order to satisfy the conditions set forth in the classical Noh problem, we find that the solution for the flow is given by a transcendental algebraic equation in the shocked density. We specialize to the modified Tait EOS in water as an example in order to see how the shock speed and shocked density, pressure, and specific internal energy change with the initial inflow velocity.