What mass of hydrogen are required to create 0.75 mol of NH3?

D)can be increased in a closed system

Ithink its solid. hope this

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.