Biofuel is an energy resource that is advantageous because it causes less pollution. biofuels come from - a rocks that have been changed by heat and pressure. b plants and animals c geothermal energy d hydroelectric energy.

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.)