Question

5. In part D, there are two sources of Ca2+ in the solution. The first part of the Ca2+ comes from the CaCl2 solution and the other comes from the Ca(OH)2 dissolved from the original solid.

a.) Determine the Ca2+ amount that came from the CaCl2 solution concentration.

b.) Determine the Ca2+ amount for the dissolved Ca(OH)2 contribution (remember from the chemical equation and equilibrium that for the dissolved Ca(OH)2 the [Ca2+]=1/2[OH].

The concentration of CaCl2 solution is 0.010M CaCl2 . We used 1g of Ca(OH)2.

Answer 1

a)

One mole CaCl₂ contains one mole Ca²⁺ and 2 moles Cl^- ions.

CaCl₂   ------> Ca²⁺ + 2 Cl^-

So, the concentration of Ca²⁺ is equal to the concentration fo CaCl₂.

Therefore, the amount of Ca²⁺ that came from 0.010 M CaCl₂ is 0.010 M.

(b)

One mole Ca(OH)₂ contains one mole Ca²⁺ and 2 moles OH^- ions.

Ca(OH)₂   -----> Ca²⁺ + 2 OH^-

So, the number of moles of Ca²⁺ is equal to the number of moles of Ca(OH)₂.

Moles of Ca(OH)₂  = mass of Ca(OH)₂ / molar mass of Ca(OH)₂

= 1 g/ (74.093 g/mol)

= 0.0135 mol

So, the number of moles of Ca²⁺ is 0.0135 mol.

Mass of Ca²⁺ = moles of Ca²⁺ x atomic mass of Ca

= 0.0135 mol x (40.078 g/mol)

= 0.54 g

Therefore, the amount of Ca²⁺ is 0.54 g.