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!

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.