Au thin films were deposited onto a Pd(111) signal crystal via physical vapor deposition (PVD). The film growth was found to proceed via a layer-by-layer fashion (Frank-van der Merwe mode). The surface composition was investigated using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) at various temperatures. Au diffuses into the Pd bulk to form an alloy at ~680 K. The adsorption and reaction of a number of small molecules including CO, ethylene, acetic acid and vinyl acetate was also studied on these surfaces. It was found that the reactivity of these surfaces vary as a function of Au/Pd atomic ratio of the surface, which can be modified simply by annealing the Au/Pd(111) to various temperatures.