Why are scientific theories changed but never thrown away?

Which of the following is considered a benefit to using wind energy as a source of power

One of the reactions in a blast furnace used to reduce iron is shown above. how many grams of fe2o3 are required to produce 15.5 g of fe if the reaction occurs in the presence of excess co? a.11.1 g b.22.1 g c.30.0 g d.44.2 g

The balanced chemical equation for this lab is: 3cucl2(aq) + 2al(s) 3cu(s) + 2alcl3(aq) if 10.5 g copper chloride react with 12.4 g aluminum, what is the limiting reactant?