   Chapter 21, Problem 102GQ

Chapter
Section
Textbook Problem

Calcium fluoride can be used in the fluoridation of municipal water supplies. If you want to achieve a fluoride ion concentration of 2.0 × 10−5 M, what mass of CaF2 must you use for 1.0 × 106 L of water? (Ksp for CaF2 is 5.3 × 10−11.)

Interpretation Introduction

Interpretation:

To calculate the mass of CaF2 must use for 1×106L of water.

Concept introduction:

Solubility product constant (Ksp) is equilibrium constant is defined for equilibrium between a solid and its respective ions in a solution.

The ionization of CaF2 in water is written as,

CaF2(s)Ca+2(aq)+2F(aq)

The Solubility product constant (Ksp) for CaF2 is written as,

Ksp=[Ca+2][2(F)]2 (1)

Numberofmoles=MassMolecularmassMass=Numberofmoles×Molecularmass

Explanation

The mass of CaF2 must use for 1×106L of water is calculated below.

Given:

The Solubility product constant (Ksp) for CaF2 is 5.3×1011.

The volume of water is 1×106L.

The concentration of fluoride ion in solution is 2×105M.

The molecular weight of CaF2 is 40gmol1.

Substitute the value of Solubility product constant (Ksp) for CaF2 and concentration of fluoride ion in equation (1) to calculate the concentration of calcium ion in the solution,

5.3×1011=[Ca+2][2(2×105M)]2[Ca+2]=0.033M

The concentration of calcium ion is equal to the concentration of CaF2. Therefore, the concentration of CaF2 is 0.033M.

The number of moles of CaF2(nCaF2) is equal to the product of the concentration of CaF2 and volume of water

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started

As natural constituents of foods, phytochemicals are safe to consume in large amounts. T F

Nutrition: Concepts and Controversies - Standalone book (MindTap Course List)

Where would you go on Earth to have a celestial pole at your zenith?

Horizons: Exploring the Universe (MindTap Course List)

9-82 What is the ground state of a nucleus?

Introduction to General, Organic and Biochemistry 