When the products of a reaction are hotter than the reactants:

the reaction is exothermic.
the reaction is endothermic.
the reactants lost internal energy.
the change in enthalpy is positive.

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.)