Iron(iii) oxide is formed when iron combines with oxygen in the air. how many grams of fe2o3 are formed when 25.9 g of fe reacts completely with oxygen? 4fe(s) + 3o2(g) > 2fe2o3(s)

a.12.0g b. 25.0g c. 37.0g d. 49.0g

The balanced chemical reaction would be

4Fe(s) + 3O2(g) ---> 2Fe2O3(s) 

We are given the amount of Fe to be used in the reaction. We use this as the starting point for the calculations. We do as follows:

25.9 g Fe (1 mol / 55.85 g) ( 2 mol Fe2O3 / 1 mol Fe ) (159.69 g / mol ) = 262.48 g Fe2O3 produced

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.