If 120 grams of aluminum oxide reacts with 100 grams of magnesium, which reactant is in excess and by how much? Al2O3 + 3Mg —> 3MgO + 2Al

Limiting reactant is magnesium.

14.1 g remain unreacted.

Explanation:

Hello!

In this case, given the balanced chemical reaction, we are able to compute the moles of each reactant by using their molar masses:

Now, since they are reacting based on a 1:3 mole ratio, we can compute the moles of magnesium consumed by the 1.18 moles of aluminum oxide as follows:

Meaning there are more available moles of magnesium than consumed, and therefore it is the limiting reactant. Moreover, it is in excess by:

It means that 14.1 g of magnesium remain unreacted.

Regards!

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72