5. In part D, there are two sources of Ca2+ in the solution. The first part of t

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.

Explanation / Answer

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.

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