Question

You are given a 1.55 g mixture of calcium nitrate and calcium chloride. You dissolve this mixture in 20 mL of water and add an excess of 0.300 M silver nitrate. You collect and dry the resulting precipitate and determine it has a mass of 0.535 grams. Calculate the percent calcium chloride in the original mixture.

Answer 1

13.4 (w/w)% of CaCl₂ in the mixture

Step-by-step explanation:

All the Cl⁻ that comes from CaCl₂ (Calcium chloride) will be precipitate in presence of AgNO₃ as AgCl.

To solve this problem we must find the moles of AgCl = Moles of Cl⁻. As 2 moles of Cl⁻ are in 1 mole of CaCl₂ we can find the moles of CaCl₂ and its mass in order to find mass percent of calcium chloride in the original mixture.

Moles AgCl - Molar mass: 143.32g/mol -:

0.535g * (1mol / 143.32g) = 3.733x10⁻³ moles AgCl = Moles Cl⁻

Moles CaCl₂:

3.733x10⁻³ moles Cl⁻ * (1mol CaCl₂ / 2mol Cl⁻) = 1.866x10⁻³ moles CaCl₂

Mass CaCl₂ -Molar mass: 110.98g/mol-:

1.866x10⁻³ moles CaCl₂ * (110.98g/mol) = 0.207g of CaCl₂ in the mixture

That means mass percent of CaCl₂ is:

0.207g CaCl₂ / 1.55g * 100 =

13.4 (w/w)% of CaCl₂ in the mixture