The flask is then cooled to 273 K, at which temperature the pressure in the flask is 508 Torr. Determine the percentage of arsine that has decomposed. A sample of gaseous arsine, AsH3, in a rigid 500 mL flask at 300 Torr and 223 K, is heated to 473 K, at which the temperature arsine decomposes to hydrogen gas and solid arsenic.