Question

How many ions form when 39 grams of calcium fluoride are added to excess water? a. 0.50 mol b. 1.0 mol c. 1.5 mol d. 3.0 mol

Answer 1

Answer:

1.5 mol ions

Explanation:

Answer 2

Answer:

c. 1.5 mol

Explanation:

• Firstly, we need to calculate the no, of moles of 39.0 grams of calcium fluoride.

n = mass / molar mass = (39.0 g) / (78.07 g/mol) = 0.499 mol ≅ 0.5 mol.

• CaF₂ ionized in water as:

CaF₂ → Ca⁺² + 2F⁻.

Every 0.1 mole of CaF₂ is ionized to 3 ions (1 ion of Ca⁺² and 2 ions of F⁻).

So, 0.5 mol of CaF₂ will contain (3 x 0.5 mol = 1.5 mol) of ions.

Thus, the right choice is "c. 1.5 mol".