1.10 atoms of aluminum reacts with 6 molecules of oxygen gas to produce aluminum oxide.

4 Al + 3 02-> 2 Al2O3

How many atoms or molecules of the excess reactant remain?

a. 2 atoms

b. 6 molecules

c. 10 atoms

d. 3 molecules

Answer: Option A) 2 atoms

Explanation:

4Al + 302 - --> 2Al2O3

4 moles of Al reacts with 3 molecules of O2

So 1.10 moles of Al should reacts with Z molecules of O2 (Assume Z is unknown)

i. e 4 moles of Al = 3 molecules of O2

4 moles of Al = 6 atoms of O2 (since 1 molecule of oxygen has two atoms of oxygen)

1.10 atoms of Al = Z atoms of O2

To get the value of Z, cross multiply

Z x 4 moles = 6 atoms x 1.10 moles

4Z = 6.6

Divide both sides by 4

4Z/4 = 6.6/4

Z = 1.65 atoms (approximately 2 atoms)

Thus, 2 atoms of the excess reactant oxygen remains.