If a receiver travels 54 yd in 9 seconds what is his average speed

Dumbledore explains that a spectator ion is an ion which is not involved in the reaction under consideration. though snape thinks you all should know sometimes it seems snape would rather be teaching another or even be head of the anyway, which is a spectator ion involved in the reaction of k2cro4(aq) and ba(no3)2(aq)?