Localized surface plasmon resonances (LSPR), the coherent oscillation of conduction band electrons confined to a nanoparticle, can be both sense and enhance electrochemical processes occurring at a metal nanoparticle surface. The spectrum of light scattered by a plasmonic nanoparticle is dependent on the properties of the LSPR. The LSPR frequency and lifetime depend on the local environment and nanoparticle morphology. Changes in refractive index, charge density, size, shape, and more can be measured through single plasmonic nanoparticle scattering spectra. In this work, single plasmonic nanoparticle spectroscopy is combined with electrochemistry to optically study various electrochemical processes on plasmonic nanoparticles. At less positive potential, the effect of charge density tuning on gold nanoparticle (AuNP) LSPRs was isolated from the effect of reactive halide anion adsorption. The capacitive charging regime was then used to study the nanoparticle morphology effects on sensitivity to change in charge density. As positive potential and anion reactivity were increased, anion adsorption and AuNP dissolution reactions occurred. The onset of these adsorption and dissolution reactions at single nanoparticles was determined by correlating spectral shifts with electrochemical potential. Plasmonic enhancement of the dissolution reaction was studied by comparing dissolution onset potential and rate with and without plasmon excitation.