When a reaction is reversible, eventually the rates of the forward and reverse actions will be equal. which of the following best explains what this means?

The answer for #3 is c but i don't know why

12. complete each of the following word equations for synthesis reactions. a. sodium + oxygen -> b. magnesium + fluorine -> 13. complete and balance the equations for the decomposition reactions. a. hgo -> [with the triangle heat symbol above the arrow] b. h2o(l) -> [with "electricity" written above the arrow]

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.