Calcium oxide reacts with water in a combination reaction to produce calcium hydroxide: CaO (s) + H₂O (l) → Ca(OH) ₂ (s)
A 4.00-g sample of CaO is reacted with 3.86 g of H₂O. How many grams of water remains after completion of reaction?

Question

Quizplus · Accepted Answer

First, we need to determine the limiting reactant using stoichiometry.

4.00 g CaO x (1 mol CaO/56.077 g CaO) x (1 mol H2O/1 mol CaO) x (18.015 g H2O/1 mol H2O) = 1.286 g H2O

3.86 g H2SO4 x (1 mol H2SO4/98.079 g H2SO4) x (1 mol CaO/1 mol H2SO4) x (1 mol H2O/1 mol CaO) x (18.015 g H2O/1 mol H2O) = 0.722 g H2O

Since CaO is the limiting reactant (produces less product), only 1.286 g H2O can be produced. Therefore, the remaining water is:

3.86 g H2O - 1.286 g H2O = 2.57 g H2O

The answer is (C) 2.57.

Calcium Oxide Reacts with Water in a Combination Reaction to Produce