Write the net ionic equation for the equilibrium that is established when ammonium bromide is dissolved in water. (use h3o instead of h .)

NH4Br is a strong electrolyte. In water, it dissociates 100% to give:
NH4Br (s)---> NH4+ (aq) + Br- (aq)

Br- is the anion of the strong acid HBr, so it is neutral. 

NH4+ is the cation of the weak base NH3. It donates a proton to water producing an ACIDIC solution.

The equilibrium reaction that takes place is:
NH4+(aq) + H2O ---> H3O+(aq) + NH3(aq)

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.