Many metals react with oxygen gas to form the metal oxide. For example, calcium reacts in the following manner

Question

Many metals react with oxygen gas to form the metal oxide. For example, calcium reacts in the following manner.
2 Ca(s) + O2(g) 2 CaO(s)

You wish to calculate the mass of calcium oxide that can be prepared from 4.07 g Ca and 2.55 g O2.
(a) How many moles of CaO can be produced from the given mass of Ca?
_______ mol

(b) How many moles of CaO can be produced from the given mass of O2?
_____ mol
(c) Which is the limiting reactant?
Calcium or Oxygen

(d) How many grams of CaO can be produced?
______ g

Answer 1

To do this, you must convert your masses to g-atoms and moles.
So you divide 4.07 g by the atomic weight of Ca, and 2.55 g by the atomic weight of the O2 dimer.
a. The equation says that 1 mole of Ca provides 1 mole of CaO. So answer- g-atoms of Ca
b. The equation says the 1 g-atom of the dimer provides 2 moles of CaO. So find the g-atoms of O2 from above and multiply by 2 to get answer.
c. The limiting reactant is the one that produces the LEAST moles of CaO in a or b.
d. This is the product of the mole wt of CaO times the least moles of CaO from a or b.