Some please please help me with 3-5 I don’t know what I’m doing brainiest answer too anyone who helps me first Earth Science btw

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]

What is the percent by mass of oxygen in fe2o3

How many moles of no2 will form when 3.3 moles of cu are reacted with excess hno3?