Question

How many moles of calcium hydroxide are needed to produce 73.7 milliliters of water, if the density of water is 0.987 g/mL? Show all steps of your calculation as well as the final answer. HCl + Ca(OH) 2 → H2O + CaCl2

Answer 1

We first balance the equation. It will now become:
2HCl + Ca(OH)₂ ⇒ 2H₂O + CaCl₂

We also calculate the molar mass of H₂O:
2 x H = 1 g x 2 = 2g
O = 16 g
molar mass of H₂O = 18 g/mol

Then using dimensional analysis:
73.7 mL H₂O x (0.987 g H₂O/1 mL H₂O) x (1 mol H₂O/18 g H₂O)
x (1 mol Ca(OH)₂/2 mol H₂O) 

= 2.02 mol Ca(OH)₂