is it A ???????

Question

Consider that calcium metal reacts with oxygen gas in the air to form calcium oxide. Suppose 6.09 mol of calcium is reacted with 4.00 mol of oxygen gas. Determine the number of moles of oxygen left over after the reaction is complete.

a. 4.00 mol oxygen

b. 3.05 mol oxygen

c. 2.09 mol oxygen

d. None of these

e. 0.96 mol oxygen

Answer 1

I don't think the answer it (a). See below...

2Ca(s) + O2(g) ==> 2CaO(s) ... balanced equation

6.09 mol Ca is limiting because it takes 2 mols Ca per 1 mol O2 so you'd need 8 mols Ca to react with 4 mols O2.

6.09 mol Ca x 1 mol O2 / 2 mols Ca = 3.05 mols O2 used up

mols O2 left over = 4.00 mols - 3.05 mols = 0.96 mols O2 left over (Answer e)