lab 5 - copper cycle Flashcards
what is the purpose of the copper cycle experiment?
a series of reactions that start and end with metallic copper
what types of reactions are involved in the copper cycle?
redox, precipitations, decomposition, and acid-base reactions
what has is evolved in the first step of the copper cycle, and why is caution required?
nitrogen dioxide, a toxic gas, is evolved. work must be done in a fume hood to avoid inhalation
why is pH adjustment important in the second step of the cycle?
to ensure the formation of Cu(OH)2 precipitate without excess HNO3, which could prevent full precipitation
what observation confirms the decomposition of Cu(OH)2 to CuO in the third step?
a colour change from blue to black indicates the formation of CuO
why is magnesium added in the fifth step?
to reduce CuSO4 to metallic copper by displacing copper from the solution
why is centrifugation used in this experiment?
separate solid products from liquid supernatants during multiple steps of the cycle
what colour change is observed in metallic copper?
reddish-brown
what colour change is observed in Cu(NO3)2?
blue solution
what colour change is observed in Cu(OH)2?
blue precipitate
what colour change is observed in CuO?
black solid
what colour change is observed in final copper?
reddish brown solid
