How many atoms of Al
are needed to react with
34.5 grams of O2 gas?
4Al + 3O2 → 2Al2O3

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 is the mass of 8 moles of sodium atoms

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.