Which is true of a mechanical wave? a) it must have a medium. b) it must travel in empty space. c) both sound and light are examples. d) it can travel in a vacuum.

Nacidified solution was electrolyzed using copper electrodes. a constant current of 1.18 a caused the anode to lose 0.584 g after 1.52 ✕ 103 s. given that the charge of an electron is 1.6022 ✕ 10−19 c, calculate avogadro's number. assume that copper is oxidized to cu2+ ions.