Which reactant is present in excess if 10.0 g of CaO react with 3.0 mol of H₂O? CaO + H₂O → Ca(OH)₂

Question

Quizplus · Accepted Answer

To determine which reactant is present in excess, we need to first calculate the amount of each reactant required for the given reaction. From the balanced chemical equation, we see that 1 mol of CaO reacts with 1 mol of H₂O to produce 1 mol of Ca(OH)2.

We are given the mass of CaO as 10.0 g, which we can convert to moles using the molar mass of CaO:
10.0 g CaO x (1 mol CaO / 56.08 g CaO) = 0.178 mol CaO

We are also given the number of moles of H₂O as 3.0 mol.

Since 1 mol of CaO reacts with 1 mol of H₂O, we can use the amount of H₂O to determine the amount of CaO required for the reaction:
3.0 mol H₂O x (1 mol CaO / 1 mol H₂O) = 3.0 mol CaO

Comparing the actual amount of CaO used (0.178 mol) to the amount of CaO required (3.0 mol), we can see that CaO is the limiting reactant and H₂O is present in excess. Therefore, the answer is C) H₂O.

Which Reactant Is Present in Excess If 10