In a galvanic cell in which the following spontaneous reaction takes place, what process

occurs at the cathode?
3Ce4+(aq) + Cr(s)  3Ce3+(aq) + Cr3+(aq)

At the cathode of a galvanic cell, reduction occurs. In this case, the Ce4+ ions are being reduced to Ce3+ ions. Therefore, the process occurring at the cathode is the reduction of Ce4+ ions to Ce3+ ions.