Helppp me pls

Which formula equation represents the burning of sulfur to produce sulfur dioxide? s(s) + o2(g) 4502(9) 2h2s(s) + 302(g) —> 2h20(0) + 2502(9) 4fes2+1102 —> 2fe2o3 + 8502 2802(g) + o2(9) v205 , 2503(9)

What is a substance? a. a physical property of matter b. a chemical property of matter c. an element or compound that cannot be physically separated d. characteristics used to tell the difference between mixtures

Concentrations expressed as a percent by mass are useful when the solute is a a. liquid b. gas c. solid