A pure sample of a monoprotic acid is dissolved in water. the sample is titrated with sodium hydroxide solution. at the point where 20.0 ml of the naoh solution has been added, the ph is 4.15. the phenolphthalein endpoint of the titration is observed when 50.0 ml of naoh have been added. what is the pka of the acid

Island arcs island arcs are long, curved chains of oceanic islands associated with seismic activity and mountain-building processes at certain plate boundaries. they occur where oceanic tectonic plates collide. along one side of these island arcs, there is usually a long, narrow deep-sea trench. at island arcs, the denser plate is subducted and is forced into the partially molten mantle under the less dense plate. the islands are composed of the extrusive igneous rocks basalt and andesite. the basalt originates most likely from the plastic mantle. the andesite originates most likely from the melting of parts of the descending plate and sediments that had accumulated on its surface. which list identifies minerals present in andesite from the greatest percentage by volume to the least percentage by volume?