If you have 2 water molecules together, would you expect them to sit "hydrogen by hydrogen" or "hydrogen to oxygen"? Why?

"hydrogen to oxygen"

Explanation:

Hydrogen bonds are formed when hydrogen is bonded to highly electronegative element such as Chlorine, fluorine, oxygen etc.

In hydrogen bonding, the hydrogen atom of one molecule of water is attracted to the oxygen atom of another molecule of water via permanent dipole-dipole interaction.

Hence, If you have 2 water molecules together, they always sit "hydrogen to oxygen" as a result of dipole - dipole interaction and  hydrogen bonding between water molecules.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g