What is the mass of 4.5 moles of sodium fluoride?

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

Can someone me with 3 and 4 plz. this is for masteries test.

What is the oxidation state of an individual bromine atom in nabro3?