Why is the covalent bond between two atoms of the same element a nonpolar bond?

Esign techniques and materials that reduce the negative environmental impact of a structure are referred to as

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.)

What does the mass of 0.7891 mol of ferric oxide (fe2o3)