What happens when a pure substance undergoes a chemical change?

How many grams of naoh are needed to make 0.250 liter of a 0.500 m solution of naoh? 0.125 g 5.00 g 2.00 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?

Draw the skeletal structures of two different molecules that are each made of 5 carbon atoms and 12 hydrogen atoms.